Fireproofing material for inhibiting spontaneous combustion of coal pile and application thereof

Abstract

The application discloses a fireproof and extinguishing material for inhibiting internal oxidation spontaneous combustion of a coal pile and application thereof. The fireproof and extinguishing material comprises two components: the first component is a mixed suspension formed by compounding superfine coal powder and a water-soluble polymer prepolymer, the superfine coal powder is a main solid component and is taken from a target coal pile, and the water-soluble polymer prepolymer is uniformly wrapped on the surface of the coal powder particles; and the second component is a water solution containing a crosslinking agent. In application, the first component is atomized and sprayed onto the surface of the coal pile, and the coal powder wrapped with the prepolymer is infiltrated into surface pores after standing and penetration; then the second component is atomized and sprayed, the crosslinking agent and the prepolymer are subjected to in-situ crosslinking reaction, adjacent coal powder particles are connected and anchored, and a three-dimensional network oxygen isolation layer with the coal powder as a continuous phase main body and the crosslinked polymer as a bonding bridge is formed. The application adopts a two-component step-by-step penetration and in-situ crosslinking film forming mode, solves the technical contradiction between the penetration and the film forming property, the oxygen isolation layer is homologous to the coal pile and does not affect the original coal calorific value, all components are green and environmentally-friendly, combustion does not release harmful gas, construction is simple, and the application is suitable for fireproof and extinguishing treatment of various open coal piles and coal storage yards.

Description

Technical Field

[0001] This invention belongs to the field of coal pile spontaneous combustion prevention technology, specifically relating to a fire prevention and extinguishing material and its application for inhibiting internal oxidation and spontaneous combustion of coal piles. Background Technology

[0002] Spontaneous combustion of coal piles is a common safety hazard during coal storage and transportation. Coal in open-air coal piles and storage silos is exposed to air for extended periods, undergoing a slow oxidation reaction with oxygen. This accumulation of heat causes the temperature to gradually rise, eventually leading to spontaneous combustion. Spontaneous combustion not only causes significant losses of coal resources, reducing its calorific value and economic worth, but also releases large amounts of harmful gases, polluting the atmosphere and, in severe cases, even causing fires that threaten the safety of coal storage areas and surrounding regions.

[0003] Currently, commonly used methods for preventing spontaneous combustion of coal piles in engineering practice are mainly divided into two categories: physical isolation and chemical inhibition. Physical isolation technologies include fine coal covering, felt covering, coal pile compaction, and fly ash slurry spraying, which inhibit the oxidation process by blocking the contact between oxygen and the coal. For example, CN119144347A discloses a fire-fighting material composed of fly ash slurry and composite colloid, which forms a covering layer on the surface of the coal pile by spraying. However, after the fly ash slurry is sprayed, the moisture evaporates quickly, and the slurry shrinks and cracks, forming new air leakage channels, resulting in poor long-term oxygen isolation effect. Moreover, the introduction of fly ash can affect the coal quality and calorific value. Chemical inhibition technologies, such as halide inhibitors, polymer inhibitors, and three-phase foam, delay the oxidation process by absorbing moisture and isolating oxygen or capturing free radicals. CN115109601A discloses an environmentally friendly flame retardant that uses yellow ash resin as a binder and is compounded with solid additives such as power plant boiler fly ash, coal gangue, or coal slime to form a dense protective layer. However, the aforementioned chemical inhibition technologies all introduce a large amount of exogenous organic or inorganic substances (such as soy protein isolate, dextrin gum, xanthophyll resin, fly ash, coal gangue, etc.). After the covering layer is mixed with coal, it will increase the ash content and reduce the calorific value. Furthermore, some materials (such as brine salts) are corrosive to the equipment or difficult to biodegrade, posing potential environmental pollution risks.

[0004] In summary, existing technologies for preventing spontaneous combustion of coal piles generally suffer from problems such as the covering material being of a different material from the coal pile, affecting the calorific value and coal quality after coal is mixed in, poor permeability of the covering layer resulting in only a thin surface layer, incomplete oxygen isolation, and insufficient long-term effectiveness. Therefore, there is an urgent need to develop a new type of fire prevention and extinguishing material that is homologous to the coal pile, has strong permeability, good film-forming properties, is environmentally friendly, and does not affect the calorific value of the coal. Summary of the Invention

[0005] One of the objectives of this invention is to provide a fire-prevention and extinguishing material that inhibits spontaneous combustion of coal piles. This material uses ultrafine coal powder from the target coal pile itself as the main component. Through two-component stepwise spraying and in-situ chemical cross-linking reaction, a three-dimensional network oxygen barrier layer with coal powder as the main continuous phase is formed inside the pores on the surface of the coal pile. This solves the technical problems of prominent contradiction between the permeability and film-forming properties of existing covering materials, the impact of heterogeneous materials on the calorific value of coal, and environmental pollution.

[0006] The second objective of this invention is to provide the application of the above-mentioned fire prevention and extinguishing material in the prevention and control of spontaneous combustion in coal piles. The process steps are simple, the construction is flexible, and it is compatible with conventional spraying equipment. It can achieve a synergistic effect of deep penetration and firm film formation. The oxygen barrier layer of this material is of the same origin as the coal pile and can be directly mixed into the coal to be used later without affecting the calorific value. Moreover, all components are green and environmentally friendly, and no harmful gases are released during combustion. It is suitable for fire prevention and extinguishing management of various open coal piles and coal storage yards.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a fire-prevention and extinguishing material for inhibiting spontaneous combustion of oxidation inside a coal pile, the fire-prevention and extinguishing material comprising a first component and a second component stored separately; The first component is a mixed suspension composed of ultrafine coal powder and water-soluble polymer prepolymer. The ultrafine coal powder is the main solid component of the first component, and the water-soluble polymer prepolymer acts as a binder to uniformly coat the surface of the ultrafine coal powder particles. The second component is an aqueous solution containing a crosslinking agent; In this process, after the first component and the second component are sprayed onto the surface of the coal pile and come into contact with each other, the crosslinking agent initiates a crosslinking reaction of the water-soluble polymer prepolymer, which connects and anchors adjacent ultrafine coal powder particles, forming a three-dimensional network oxygen barrier layer in situ with ultrafine coal powder as the continuous phase and crosslinked polymer as the bonding bridge.

[0008] Preferably, in the first component, the mass percentage of the ultrafine coal powder is 30%~70%, the mass percentage of the water-soluble polymer prepolymer is 1%~10%, and the remainder is water; the ultrafine coal powder is taken from the target coal pile to be subjected to fire prevention and extinguishing treatment, and the particle size D90 is ≤30μm after grinding.

[0009] Preferably, the water-soluble polymer prepolymer is selected from one or more of hydroxypropyl methylcellulose, sodium alginate, polyvinyl alcohol, and polyacrylamide.

[0010] Preferably, in the second component, the crosslinking agent is selected from one or more of borax, organoboron crosslinking agent, and aluminum citrate, and the mass concentration of the crosslinking agent in the second component is 0.1% to 0.5%.

[0011] Preferably, the first component further comprises a biodegradable surfactant, wherein the surfactant is selected from alkyl glycosides or rhamnolipids, and the amount of surfactant added is 0.05% to 0.5% of the total mass of the first component.

[0012] Secondly, the present invention provides the application of the above-mentioned fire-preventing and extinguishing material in suppressing spontaneous combustion of oxidation inside coal piles. The application includes sequentially spraying the first and second components of the fire-preventing and extinguishing material onto the surface of open-air coal piles or coal storage piles. After the second component penetrates into the pores of the coal pile, it undergoes a cross-linking reaction with the water-soluble polymer prepolymer in the first component that is coated on the surface of ultrafine coal powder. The cross-linked polymer connects and anchors adjacent ultrafine coal powder particles through chemical bonds. The ultrafine coal powder, as a continuous skeleton, fills the entire oxygen barrier layer and is tightly bonded to the lower coal pile through the interlocking action of homologous coal powder, ultimately forming a bonded oxygen barrier layer with coal powder as the main body.

[0013] The ultrafine coal powder in the bonding oxygen barrier layer is of the same origin as the coal in the lower coal pile. The bonding oxygen barrier layer can be directly mixed into the coal to be used later, and its impact on the calorific value of the raw coal is ≤1%. Moreover, the cross-linked polymer can be completely decomposed during the coal combustion process, and no harmful gases are released.

[0014] Preferably, in specific applications, the following steps are included: S1. First spraying: The first component is sprayed evenly onto the surface of the coal pile in atomized form, with a single spraying volume of 2~5L / m². 2 Allow it to stand and infiltrate for 0.5 to 4 hours to allow the ultrafine coal powder coated with polymer prepolymer to fully penetrate into the pores of the coal pile surface; S2. Second spraying: The second component is sprayed evenly onto the surface of the same coal pile in atomized form, with a single spraying rate of 1~3 L / m². 2 Let it stand still for 4 to 24 hours.

[0015] Preferably, the first component is sprayed using an airless sprayer or a dual-fluid spraying system, with a nozzle orifice diameter ≥1.2mm and a spraying pressure of 0.5~2.0MPa; the storage tank of the first component is equipped with a mechanical stirring device to continuously maintain the uniform suspension state of the ultrafine coal powder.

[0016] Preferably, the second component is sprayed using a fan-shaped nozzle at a pressure of 0.3~1.5MPa.

[0017] Preferably, for the coal pile slope area, the surface of the coal pile is pre-wetted by low-pressure water spraying before step S1.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. In the fire-resistant and extinguishing material of this invention, the ultrafine coal powder is taken from the target coal pile to be treated for fire prevention and extinguishing, and after grinding, it serves as the main solid component of the first component (30%~70% by mass). In the formed bonding and oxygen-barrier layer, the ultrafine coal powder serves as the main continuous phase, tightly bonded to the underlying coal pile through homogeneous interlocking. The overall quality of the covering layer is consistent with that of the coal pile itself, requiring no separation treatment, and can be directly mixed into the coal to be used subsequently, with an impact on the calorific value of the raw coal not exceeding 1%. Compared with the existing technology that uses inorganic materials such as fly ash, cement, and water glass, or organic materials such as soybean protein and polyacrylamide as the main components of the covering material, this invention fundamentally avoids the problem of increased ash content and decreased calorific value caused by the mixing of heterogeneous materials into the coal, achieving "coal-based coal treatment and homogeneous covering," and solving the technical problem of heterogeneous materials reducing the calorific value of coal.

[0019] 2. Existing covering materials, in order to achieve film-forming effects, typically have high viscosity, making it difficult to penetrate the pores of the coal pile surface. They can only form a thin surface layer with limited oxygen barrier effect. If the viscosity is reduced, the film-forming properties are poor, and a continuous oxygen barrier layer cannot be formed. This invention designs the fire-extinguishing material into two independently stored components, both of which are low-viscosity aqueous solutions or suspensions (viscosity ≤ 50 mPa·s) before spraying, possessing excellent penetration performance. The first component, sprayed first, can fully penetrate into the pores of the coal pile surface to a depth of 10-20 mm. The second component, sprayed subsequently, also has good penetration. After the two components meet in the pores of the coal pile, a slow chemical cross-linking reaction occurs, and the system viscosity gradually increases to 500-5000 mPa·s within 1-12 hours, forming a deep, dense, and continuous three-dimensional network oxygen barrier layer in situ. This reaction sequence control mode takes into account both the penetration during the initial construction phase and the film-forming properties after curing, overcoming the technical contradiction in existing technologies where "high viscosity makes penetration difficult and low viscosity prevents film formation."

[0020] 3. In this invention, ultrafine coal powder is not only a filler but also the continuous phase substrate of the oxygen barrier layer. In the first component, a water-soluble polymer prepolymer acts as a binder, uniformly coating the surface of the ultrafine coal powder particles. After the second component is incorporated, a crosslinking agent initiates a crosslinking reaction in the prepolymer. The crosslinked polymer directly connects and anchors adjacent ultrafine coal powder particles through chemical bonds, forming a three-dimensional network structure with coal powder as the skeleton and crosslinked polymer as the bonding bridge. Compared with the "encapsulation type" structure of polymer network coating coal powder particles in the prior art, the "connection type" structure of this invention, in which coal powder acts as the continuous phase substrate (addition amount 30%~70%), not only significantly reduces the amount of polymer material used, saving costs, but also provides rigid connections between coal powder particles through chemical bonds. The oxygen barrier layer has higher compressive strength, wind erosion resistance, and structural integrity, and can withstand natural weathering and external damage for a long time.

[0021] 4. The water-soluble polymer prepolymers (hydroxypropyl methylcellulose, sodium alginate, polyvinyl alcohol, polyacrylamide, etc.) selected in this invention are all biodegradable or low-toxicity and harmless materials; the crosslinking agents selected are borax, organic boron crosslinking agents, and aluminum citrate, avoiding the corrosiveness of halide crosslinking agents such as calcium chloride and magnesium chloride to equipment and the pollution to soil and water bodies; the surfactants selected are alkyl glycosides or rhamnolipides, which are biodegradable green surfactants, different from the difficult-to-degrade chemical surfactants such as sodium dodecyl sulfate and sodium dodecylbenzene sulfonate commonly used in the prior art, and can effectively disperse and wet solid particles such as coal powder. Although the amount of alkyl glycoside surfactants selected in this invention is only 0.05%~0.5%, it can significantly reduce the surface tension of the slurry, improve the wettability and dispersion stability of coal powder, and play an important role in ensuring the uniformity and integrity of the oxygen barrier layer. The above components can be completely decomposed during the subsequent combustion and utilization of coal, without the release of corrosive gases such as HCl and SO2 or toxic and harmful gases such as NH3, and do not cause secondary environmental pollution, which meets the requirements of green environmental protection and sustainable development.

[0022] 5. This invention employs a two-stage spraying process. The first and second components are stored independently and sprayed sequentially, eliminating the need for complex mixing and proportioning equipment on-site, making operation simple. The first component uses an airless sprayer or a dual-fluid spraying system equipped with a mechanical agitator to maintain uniform suspension of coal powder, stably spraying a high-concentration suspension with a solids content of 30%~70%. The second component can be sprayed using a conventional fan-shaped nozzle. For easily eroded areas such as coal pile slopes, low-pressure water spraying pre-wetting treatment can be performed before construction to further improve the penetration effect. The entire process has low equipment requirements, high construction efficiency, and is suitable for fire prevention and extinguishing of various open-air coal piles, coal storage silos, and coal transfer yards.

[0023] 6. This invention leverages the active oxygen-consuming characteristics of homologous ultrafine coal powder to endow the oxygen barrier layer with a unique pre-oxygen absorption and filtration function, breaking through the limitations of traditional covering materials that can only passively and physically isolate oxygen. The ultrafine coal powder is taken from the target coal pile and, after fine grinding, has a smaller particle size and higher reactivity. It can preferentially undergo a low-temperature oxidation reaction with oxygen along the path of air penetration into the depth of the coal pile, consuming the trace oxygen penetrating the covering layer in situ, forming a dynamic oxygen consumption barrier. This prevents oxygen from further penetrating into the deep pores of the coal pile from the source, cutting off the oxygen supply for deep oxidation and heat storage in the coal pile. In contrast, fly ash, inorganic mineral powder, and other heterogeneous solid media are inert materials that cannot react with oxygen, only achieving passive isolation. They are unable to suppress deep spontaneous combustion caused by the continuous penetration of trace oxygen. This invention thus achieves dual combustion suppression through physical isolation and active oxygen consumption, with a significantly better combustion suppression effect and longer duration than existing technologies. Detailed Implementation

[0024] To address the prominent contradiction between permeability and film-forming properties in existing coal pile covering materials, the impact of heterogeneous materials on coal calorific value, and the environmental pollution caused by organic materials, this invention provides a fire-resistant and extinguishing material for inhibiting spontaneous combustion and oxidation within coal piles, and its application. To verify the permeability and film-forming performance, oxygen barrier effect, impact on coal calorific value, and the mechanism of action of each component of the fire-resistant and extinguishing material of this invention, the core testing indicators set in this embodiment are: ① Oxygen barrier layer thickness: Randomly select 3 points on the surface of the coal pile, dig out a profile with a shovel, measure the continuous thickness of the covering layer, and take the average value in mm. The greater the thickness, the better the penetration depth and film formation. ② Erosion loss rate: The spray device was used to simulate a rain intensity of 10 mm / h for 1 hour. The coal dust lost by erosion was collected, dried and weighed, and the erosion loss rate was calculated (mass of lost coal dust / mass of coal dust on the surface of the raw coal pile × 100%). The lower the erosion loss rate, the stronger the rainwater erosion resistance of the cover layer. ③ Calorific value reduction rate: Take a mixed sample of the overburden layer and the underlying raw coal, measure the lower heating value on the basis, and calculate the percentage reduction by comparing it with the calorific value of the raw coal. A calorific value reduction rate of ≤1% is considered to have no substantial impact on the coal quality. ④ Construction adaptability: Observe the sprayability of the grout, penetration time and continuity of the coating after curing. The evaluation methods are visual inspection and touch.

[0025] In all the following examples and comparative examples, the source of ultrafine coal powder is: taken from the target coal pile to be treated for fire prevention and extinguishing (Shenhua mixed coal from the open coal yard of a thermal power plant), dried, crushed, ball-milled and passed through a 500-mesh standard sieve to obtain ultrafine coal powder with a particle size D90≤30μm for later use; the water-soluble polymer prepolymer is hydroxypropyl methylcellulose (HPMC, viscosity 400mPa·s, food grade); the crosslinking agent is borax (analytical grade); and the surfactant is alkyl glycoside (APG0810, biodegradability ≥98%).

[0026] First, Examples 1-6 (different amounts of ultrafine coal powder, polymer prepolymer, and surfactant), Comparative Example 1 (no crosslinking agent, i.e., only the first component is sprayed), Comparative Example 2 (the first and second components are premixed and then sprayed once), and Comparative Example 3 (fly ash is used instead of ultrafine coal powder) were set up to investigate the effects of the amount of core components added and the construction method on the thickness of the oxygen barrier layer, the erosion loss rate, and the calorific value of the coal. The test results are shown in Table 1.

[0027] Example 1 A fire extinguishing material for inhibiting spontaneous combustion of coal piles through oxidation consists of a first component and a second component that are stored independently and sprayed sequentially.

[0028] The first component (total mass 10 kg) consisted of 5 kg of ultrafine coal powder (50% by mass), 0.5 kg of hydroxypropyl methylcellulose (5% by mass), 0.025 kg of alkyl glycosides (0.25% by mass), and the remainder was water (4.475 kg). The above materials were added to a storage tank equipped with a mechanical stirrer and stirred at 300 rpm for 30 minutes to obtain a homogeneous suspension. The dynamic viscosity was measured to be 45 mPa·s.

[0029] The second component (total mass 10 kg): 0.015 kg of borax (mass concentration 0.15%), the remainder being water (9.985 kg), stirred and dissolved, and the dynamic viscosity was measured to be 1.2 mPa·s.

[0030] How to use: 1) First spraying: Use an airless sprayer (nozzle diameter 1.5mm, spraying pressure 1.2MPa) to evenly spray the first component onto the surface of the coal pile at a rate of 3L / m². 2 The mixing device in the storage tank runs continuously during spraying. Allow to stand and infiltrate for 2 hours.

[0031] 2) Second spraying: Using a fan-shaped nozzle (spraying pressure 0.8MPa), the second component is evenly sprayed onto the same area at a rate of 2L / m². 2 .

[0032] 3) In-situ cross-linking film formation: allow to stand for 12 hours.

[0033] Example 2 The difference between this embodiment and Embodiment 1 is that the amount of ultrafine coal powder added in the first component is increased to 6 kg (60%), the amount of hydroxypropyl methylcellulose added is increased to 0.8 kg (8%), the amount of alkyl glycoside is 0.03 kg (0.3%), and the amount of water is adjusted accordingly to 3.17 kg. The second component remains unchanged. The spraying amount and construction steps are the same as in Embodiment 1.

[0034] Example 3 The difference between this embodiment and Embodiment 1 is that the amount of ultrafine coal powder added in the first component is reduced to 4 kg (40%), the amount of hydroxypropyl methylcellulose added is reduced to 0.3 kg (3%), the amount of alkyl glycoside is 0.02 kg (0.2%), and the water is adjusted accordingly to 5.68 kg. The second component remains unchanged. The spraying amount and construction steps are the same as in Embodiment 1.

[0035] Example 4 The difference between this embodiment and Embodiment 1 is that the amount of ultrafine coal powder added in the first component is 7 kg (70%), the amount of hydroxypropyl methylcellulose added is 1.0 kg (10%), the amount of alkyl glycoside is 0.05 kg (0.5%), and the amount of water is adjusted accordingly to 1.95 kg. The second component remains unchanged. The spraying amount and construction steps are the same as in Embodiment 1.

[0036] Example 5 The difference between this embodiment and Embodiment 1 is that the spraying rate of the first component is 4 L / m³. 2 The second component was sprayed at a rate of 2.5 L / m². 2 The static infiltration time was extended to 3 hours, and the curing time was extended to 16 hours. The rest was the same as in Example 1.

[0037] Example 6 The difference between this embodiment and Embodiment 1 is that no surfactant is added to the first component. That is, the first component consists only of 5 kg of ultrafine coal powder (50%), 0.5 kg of hydroxypropyl methylcellulose (5%), and 4.5 kg of water. The rest of the formula and construction method are exactly the same as in Embodiment 1.

[0038] Comparative Example 1 The difference between this comparative example and Example 1 is that only the first component is sprayed, and the second component is not sprayed. That is, the first component is sprayed at 3 L / m³. 2 After spraying, let it stand for 12 hours, and the rest is the same as in Example 1.

[0039] Comparative Example 2 The difference between this comparative example and Example 1 is that the first and second components are pre-mixed according to the usage ratio of Example 1 (first component: second component = 3:2 volume ratio), and immediately sprayed in one pass using an airless sprayer after thorough mixing, with a total spray volume of 5 L / m³. 2 The rest is the same as in Example 1.

[0040] Comparative Example 3 The difference between this comparative example and Example 1 is that the ultrafine coal powder in the first component is replaced with fly ash of the same particle size (Grade II fly ash, ≤12% residue on 45μm sieve), while the rest of the formula and construction method are the same as in Example 1.

[0041] Table 1. Raw material ratios and test results for each experimental group As shown in Table 1, in Comparative Example 1, the second component (without crosslinking agent) was not sprayed, and the polymer prepolymer in the first component could not undergo a crosslinking reaction. After drying, only a loose coal powder layer was formed, without a continuous oxygen barrier layer. Under a rain intensity of 10 mm / h, the loss rate was as high as 8.5%, completely losing its protective ability. In Comparative Example 2, the first and second components were premixed and sprayed at once. After mixing, the viscosity of the system rose sharply to over 2000 mPa·s within 1 minute, resulting in extremely poor atomization. The slurry accumulated on the surface of the coal pile and could not penetrate. The resulting cover layer was less than 2 mm thick and brittle, with a scouring loss rate of 4.2%. In Comparative Example 3, fly ash was used instead of ultrafine coal powder. Although a cover layer of a certain thickness could be formed, the fly ash was heterogeneous with the coal pile body, and the cover layer had poor bonding with the underlying coal layer. The scouring loss rate was 2.0%, and the calorific value decreased by 2.3% after being mixed with coal, which had a significant adverse effect on the coal quality.

[0042] Examples 1-6 all employed a step-by-step spraying and in-situ cross-linking construction method. Both the first and second components could fully penetrate into the surface pores of the coal pile, forming a three-dimensional network oxygen barrier layer with ultrafine coal powder as the continuous phase after the cross-linking reaction. Example 1 (50% coal powder, 5% hydroxypropyl methylcellulose) formed a 10mm thick oxygen barrier layer with a scour loss rate of 0.8% and a calorific value reduction of only 0.44%. Example 2 (60% coal powder, 8% hydroxypropyl methylcellulose) increased the oxygen barrier layer thickness to 14mm, reducing the scour loss rate to 0.5% and the calorific value reduction to 0.22%. Example 4 (70% coal powder, 10% hydroxypropyl methylcellulose) achieved a 16mm thick oxygen barrier layer with a scour loss rate of 0.4% and a calorific value reduction of 0.18%. Example 5, by increasing the spraying volume and extending the penetration curing time, achieved an oxygen barrier layer thickness of 18mm with a scour loss rate of only 0.3%. In Example 6, due to the absence of surfactant, the ultrafine coal powder exhibited poor wettability in water. Even after stirring, a small amount of coal powder agglomerates remained suspended in the slurry. When sprayed onto the coal pile surface, the slurry's spreading uniformity was significantly lower than in Example 1, with localized droplet rolling and accumulation, resulting in shallow penetration and a final oxygen barrier layer thickness of only 5 mm. This indicates that the lack of surfactant increases the interfacial tension of the coal powder-water system, hindering the rapid spreading and uniform penetration of coal powder into the pores on the coal pile surface. Consequently, the oxygen barrier layer formed after the cross-linking reaction becomes thinner, less dense, and significantly less erosive. Considering both performance and cost, Example 2 represents a superior formulation. In this case, the coal powder content is moderate, and the amount of hydroxypropyl methylcellulose is sufficient to form a robust network, resulting in good economic efficiency.

[0043] Comparative Example 4 (Comparison of different crosslinking agents) To verify the effect of the type of crosslinking agent, a comparative example 4 was set up based on the formulation of Example 2: the crosslinking agent in the second component was replaced by calcium chloride (mass concentration 0.15%) instead of borax, with the rest being the same as in Example 2. Test results: the oxygen barrier layer thickness was 12 mm, the erosion loss rate was 0.6%, the calorific value reduction rate was 0.35%, and the construction adaptability was good. However, in subsequent combustion tests, when the cover layer sample was burned in an 850℃ muffle furnace, the flue gas condensate was acidic (pH=4.5), and a small amount of HCl gas was detected escaping. In contrast, the flue gas condensate of Example 2 was neutral (pH=7.0), with no corrosive gas release, indicating that borax is a better crosslinking agent, and its combustion decomposition produces no corrosive products.

[0044] Comparative Example 5 (Comparison of different surfactants) To verify the effect of surfactant type, a comparative example 5 was set up based on the formulation of Example 2: the alkyl glycoside in the first component was replaced with sodium dodecyl sulfate (SDS, 0.3% addition), and the rest was the same as in Example 2. Test results: the oxygen barrier thickness was 13 mm, the scouring loss rate was 0.5%, and the calorific value reduction rate was 0.25%, with performance close to that of Example 2. However, through biodegradability testing, the alkyl glycoside showed a 98% degradation rate after 28 days, while SDS only reached 45%, indicating that the alkyl glycoside selected in this invention has a greater environmental advantage.

[0045] Based on the test results of Examples 1-6 and Comparative Examples 1-5, the optimal formulation of the fire-fighting material of the present invention is as follows: the first component contains 60% ultrafine coal powder, 8% hydroxypropyl methylcellulose, and 0.3% alkyl glycosides; the second component contains 0.15% borax. The optimal application parameters are: the first component spraying rate is 4 L / m². 2 The second component was sprayed at a rate of 2.5 L / m². 2 The first component is allowed to stand and infiltrate for 3 hours, and the second component is sprayed and cured for 16 hours. Under these conditions, the thickness of the oxygen barrier layer formed is ≥14mm, the erosion loss rate under a rain intensity of 10mm / h is ≤0.5%, the impact on the calorific value of the raw coal is ≤0.3%, and all components are green and environmentally friendly, with no release of harmful gases during combustion.

[0046] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A fire-resistant and extinguishing material for inhibiting spontaneous combustion of coal piles due to internal oxidation, characterized in that, The fire-resistant and extinguishing material comprises a first component and a second component; The first component is a mixed suspension composed of ultrafine coal powder and water-soluble polymer prepolymer. The ultrafine coal powder is the main solid component of the first component, and the water-soluble polymer prepolymer acts as a binder to uniformly coat the surface of the ultrafine coal powder particles. The second component is an aqueous solution containing a crosslinking agent; In this process, after the first component and the second component are sprayed onto the surface of the coal pile and come into contact with each other, the crosslinking agent initiates a crosslinking reaction of the water-soluble polymer prepolymer, which connects and anchors adjacent ultrafine coal powder particles, forming a three-dimensional network oxygen barrier layer in situ with ultrafine coal powder as the continuous phase and crosslinked polymer as the bonding bridge.

2. The fire-resistant and extinguishing material for suppressing spontaneous combustion of coal piles according to claim 1, characterized in that, In the first component, the ultrafine coal powder accounts for 30% to 70% by mass, the water-soluble polymer prepolymer accounts for 1% to 10% by mass, and the remainder is water; The ultrafine coal powder is taken from the target coal pile to be subjected to fire prevention and extinguishing treatment, and the particle size D90 is ≤30μm after grinding.

3. The fire-resistant and extinguishing material for inhibiting spontaneous combustion of coal piles according to claim 1, characterized in that, The water-soluble polymer prepolymer is selected from one or more of hydroxypropyl methylcellulose, sodium alginate, polyvinyl alcohol, and polyacrylamide.

4. The fire-resistant and extinguishing material for inhibiting spontaneous combustion of coal piles according to claim 1, characterized in that, In the second component, the crosslinking agent is selected from one or more of borax, organoboron crosslinking agents, and aluminum citrate, and the mass concentration of the crosslinking agent in the second component is 0.1% to 0.5%.

5. The fire-resistant and extinguishing material for inhibiting spontaneous combustion of coal piles according to claim 1, characterized in that, The first component further includes a biodegradable surfactant selected from alkyl glycosides or rhamnolipids, and the amount of surfactant added is 0.05% to 0.5% of the total mass of the first component.

6. The application of the fire-resistant and extinguishing material according to any one of claims 1 to 5 in suppressing spontaneous combustion of coal piles, characterized in that, The application involves sequentially spraying the first and second components of the fire-fighting material onto the surface of an open-air coal pile or a coal storage bunker. After the second component penetrates into the pores of the coal pile, it undergoes a cross-linking reaction with the water-soluble polymer prepolymer in the first component that is coated on the surface of ultrafine coal powder. The cross-linked polymer connects and anchors adjacent ultrafine coal powder particles through chemical bonds. The ultrafine coal powder serves as a continuous skeleton, filling the entire oxygen barrier layer and tightly bonding with the lower coal pile through the interlocking action of homologous coal powder, ultimately forming a bonded oxygen barrier layer with coal powder as the main component.

7. The application according to claim 6, characterized in that, Includes the following steps: S1. First spraying: The first component is sprayed evenly onto the surface of the coal pile in atomized form, with a single spraying volume of 2~5L / m². 2 Allow it to stand and infiltrate for 0.5 to 4 hours to allow the ultrafine coal powder coated with polymer prepolymer to fully penetrate into the pores of the coal pile surface; S2. Second spraying: The second component is sprayed evenly onto the surface of the same coal pile in atomized form, with a single spraying rate of 1~3 L / m². 2 Let it stand still for 4 to 24 hours.

8. The application according to claim 7, characterized in that, The first component is sprayed using an airless sprayer or a dual-fluid spraying system with a nozzle orifice diameter ≥1.2mm and a spraying pressure of 0.5~2.0MPa. The storage tank of the first component is equipped with a mechanical stirring device to continuously maintain the uniform suspension of the ultrafine coal powder.

9. The application according to claim 7, characterized in that, The second component is sprayed using a fan-shaped nozzle at a pressure of 0.3~1.5MPa.

10. The application according to claim 7, characterized in that, For the coal pile slope area, before step S1, the surface of the coal pile is pre-wetted by low-pressure water spraying.

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