A high-temperature response composite material for synergistic regulation of coal pile fire resistance and heat value release, and a preparation method and application thereof

Abstract

A high-temperature response composite material for synergistic regulation of coal pile fire resistance and heat value release, and a preparation method and application thereof. The material is composed of modified inorganic particle fillers and composite high heat value carriers. The modified inorganic particle fillers include organic modified SiO2 particles and MnFe2O4 nanoparticles grafted with hydroxyl functional groups. The composite high heat value carrier is composed of polyether, polydimethylsiloxane and white oil high heat value oil phase. After treatment, the components form a uniform dispersion, stable emulsion composite system, with good seepage perfusion performance and environmental adaptability. At room temperature, the initial oxidation rate of coal is reduced by blocking the diffusion path of water and oxygen, realizing efficient fire resistance. At high temperature, the cracking and oxidation process of coal and organic carriers is accelerated by catalysis, inhibiting oil phase agglomeration and carbonization coking problems, significantly improving the burnout rate and clean combustion performance. The material system has multiple advantages such as room temperature fire resistance, high temperature combustion support and no residual carbon pollution.

Description

Technical Field

[0001] This invention relates to the field of coal storage, transportation and efficient combustion technology, specifically to a high-temperature responsive composite material for synergistic regulation of flame retardancy and calorific value release in coal piles, its preparation method and application. Background Technology

[0002] Spontaneous combustion of coal piles is a common thermal disaster during coal transportation and open-air storage, especially in port yards, railway transfer points, and open-air coal piles. Due to prolonged exposure to complex environments such as air, sunlight, and rain, fires caused by spontaneous combustion not only result in significant losses of coal resources but also seriously threaten the safety of workers and the surrounding ecological environment. Coal spontaneous combustion primarily originates from low-temperature oxidation heat accumulation. Its occurrence is characterized by its high degree of concealment, rapid development, and difficulty in early warning and control, making it one of the key technical challenges restricting the safety and economic efficiency of coal storage and transportation.

[0003] Current engineering practices often employ methods such as film covering and inhibitor spraying for coal pile flame retardant treatment. While these methods can mitigate the risk of spontaneous combustion to some extent, they generally suffer from problems such as short effective periods, significant susceptibility to climate and site conditions, and poor environmental adaptability. Some materials are prone to structural disintegration at high temperatures, leading to decreased flame retardant performance and potentially even inducing combustion-supporting effects due to improper reactions. Furthermore, traditional flame retardant methods often neglect the utilization of coal's calorific value as an energy source, making the treated coal piles difficult to burn directly and increasing subsequent cleanup and fuel processing costs. Therefore, there is an urgent need to develop a functional composite material with good environmental adaptability, high-temperature response characteristics, and synergistic calorific value regulation capabilities. This material should be able to effectively seal and inhibit oxygen and flame retard on the surface and internal pores of coal piles at room temperature, while releasing high-calorific-value components at high temperatures to improve combustion efficiency. This would achieve the dual goals of safe storage and efficient utilization, meeting the green, safe, and efficient management requirements for coal during transportation and open-air storage. Summary of the Invention

[0004] The purpose of this invention is to provide a high-temperature responsive composite material for the synergistic regulation of flame retardancy and calorific value release in coal piles, as well as its preparation method and application. The preparation method is simple and convenient, and the material cost is low. The prepared composite material has the characteristics of good high-temperature responsiveness, strong coverage and permeation capacity, high film-forming and sealing stability, and efficient catalytic calorific value release. It is suitable for open-pit coal piles, flame retardant protection during long-distance coal transportation, and high-temperature and efficient combustion of coal in coal-storage power plants.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A high-temperature responsive composite material for synergistic regulation of flame retardancy and calorific value release in coal piles, the material being composed of organically modified inorganic particulate fillers and a composite high-calorific-value carrier; the organically modified inorganic particulate fillers include organically modified SiO2 particles and MnFe2O4 nanoparticles grafted with hydroxyl functional groups, and the composite high-calorific-value carrier is composed of polyether, polydimethylsiloxane and white oil-based high-calorific-value oil phase mixed in a certain proportion.

[0007] To achieve the above-mentioned objectives, this invention also provides a method for preparing a high-temperature responsive composite material for synergistic regulation of flame retardancy and calorific value release in coal piles, comprising the following steps:

[0008] a. Add SiO2 to anhydrous ethanol and disperse it by ultrasonication. Add polyethylene glycol and stir the reaction at 40-50℃. Then wash and dry with deionized water to obtain organically modified SiO2 particles.

[0009] b. Dissolve Mn(NO3)2·4H2O and Fe(NO3)3·9H2O in deionized water, control the pH at 10-11, and stir the reaction at 70℃ until MnFe2O4 nanoparticles are fully formed and precipitated. Then, add polyvinyl alcohol and isophorone diisocyanate to the reaction system and react at 50-60℃ under nitrogen protection to obtain MnFe2O4 nanoparticles with hydroxyl functional groups grafted on the surface.

[0010] c. Add polyether and polydimethylsiloxane to a reaction vessel in proportion, and heat and stir at 60-70℃ to form a homogeneous oil phase base system; add an appropriate amount of deionized water to the homogeneous oil phase base system, and then add white oil-based high calorific value oil phase, and continue stirring at the same temperature to form a stable composite high calorific value carrier.

[0011] d. Add aromatic ether linker to the composite high calorific value carrier obtained in step c, and stir the reaction at 60-75℃ for 1-2 hours to obtain a mixed system;

[0012] e. The organically modified SiO2 particles prepared in step a and the MnFe2O4 nanoparticles grafted with hydroxyl functional groups prepared in step b are added to the mixture obtained in step d in proportion. The mixture is then emulsified at 60-75℃ for 1-2 hours under stirring to obtain a high-temperature responsive composite material for synergistic regulation of flame retardancy and calorific value release in coal piles.

[0013] Preferably, in step a, the mass ratio of SiO2 to polyethylene glycol is (0.5-2):1; the reaction is stirred for 2 hours; and the mass-to-volume ratio of SiO2 to anhydrous ethanol is 1 g: (13-32) ml.

[0014] Preferably, in step b, the mass ratio of Mn(NO3)2·4H2O to Fe(NO3)3·9H2O is 1:(1.5-2.5); the reaction is stirred for 1.5 h; and the mass-volume ratio of Mn(NO3)2·4H2O to deionized water is 1 g:(12-19) ml.

[0015] Preferably, in step b, the mass ratio of Mn(NO3)2·4H2O, polyvinyl alcohol, and isophorone diisocyanate is 10:1:(5-10); the reaction is carried out under nitrogen protection for 2 hours.

[0016] Preferably, in step c, the polyether is selected from polypropylene glycol or polyethylene glycol; the high-calorific-value oil phase of the white oil is pharmaceutical-grade mineral oil or light paraffin oil.

[0017] Preferably, in step c, the mass ratio of polyether, polydimethylsiloxane and white oil-based high-calorific-value oil phase in the composite high-calorific-value carrier is (4-14):(1-5):1.

[0018] Preferably, in step d, the aromatic ether linker is hydroquinone dihydroxyethyl ether or resorcinol-bis(β-hydroxyethyl) ether, and the aromatic ether linker accounts for 2.4-2.8% of the mass fraction of the composite high calorific value carrier.

[0019] Preferably, in step e, the organically modified SiO2 particles and the MnFe2O4 nanoparticles grafted with hydroxyl functional groups account for 6-20% and 10-15% of the mass of the mixed system, respectively.

[0020] To achieve the above objectives, the present invention also provides the application of the high-temperature responsive composite material prepared by the above preparation method for the synergistic regulation of flame retardancy and calorific value release in coal pile flame retardancy. The specific application process is as follows: the composite material is sprayed to cover the surface of coal particles to form a hydrophobic oxygen barrier, or injected into the cracks of the coal pile by pressurized injection, seeping in and sealing the air leakage channels and replacing the free oxygen inside the pile. The treated coal pile does not need to be cleaned and can be directly used for high-temperature combustion, taking into account both flame retardant stability and improved calorific value.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. Under normal temperature conditions, the low-volatility composite high-calorific-value carrier of this invention can form a uniform organic phase continuous film on the surface of coal particles, filling small pores and reducing the further diffusion of oxygen inside the pile. The carrier also has moderate thermal conductivity and higher thermal conductivity than air, which helps to conduct and diffuse heat inside the pile, spreading unabsorbed heat to the whole pile, slowing down the accumulation rate of hot spots, and avoiding local heat accumulation. At the same time, the organically modified SiO2 particles endow the system with excellent thermal reflectivity and thermal insulation shielding ability. The MnFe2O4 nanoparticles grafted with hydroxyl functional groups can inhibit the oxidation chain reaction of coal through hydrogen bonding synergy and complexation oxygen capture, further enhancing the inhibitory effect of the composite material on the heating and oxidation chain reaction inside the coal pile under normal temperature conditions.

[0023] 2. The low-volatility composite high-calorific-value carrier in this invention possesses good fluidity and permeability, and provides a certain degree of hydrophobicity, unaffected by rainwater absorption, thus preventing moisture accumulation within the coal pile. Simultaneously, the composite high-calorific-value carrier can form a stable, continuous hydrophobic oil film on the surface of coal particles to isolate oxygen penetration, and possesses a certain heat capacity, capable of absorbing some heat, preventing micro-regional heat accumulation, and slowing down the heat storage rate within the coal pile. The surface-grafted MnFe2O4 containing hydroxyl functional groups mixed in the composite high-calorific-value carrier catalytically oxidizes the coal powder and high-calorific-value carrier in high-temperature environments such as power plant blast furnaces, increasing the reaction rate and reducing the activation energy. Furthermore, the composite high-calorific-value carrier exhibits high calorific-value combustibility, which can compensate for calorific value loss during coal pile storage to a certain extent, and the combustion products are mainly CO2 and water, without significantly increasing the initial activation energy of combustion.

[0024] 3. The low-volatility composite high-calorific-value carrier in this invention, combined with the heat insulation and heat reflectivity provided by the organic modified SiO2 particles, physically encapsulates and isolates the oxygen inside the coal pile, reducing the impact on the activation energy of organic matter in the coal. At the same time, under high-temperature conditions, the presence of PDMS in the composite high-calorific-value carrier causes the complex to generate a flexible carbon layer under high-temperature conditions. The adhesion between the flexible carbon layer and the surface of the coal particles decreases, making it difficult to form a coating layer during combustion, resulting in a large amount of residual carbon.

[0025] In summary, the composite material prepared in this invention primarily inhibits the flame retardation of coal in storage scenarios such as coal storage ports. Because the coal has undergone flame-retardant treatment, high temperatures are avoided in these scenarios, thus providing long-term flame retardancy for the coal stockpile. High-temperature combustion enhancement is mainly targeted at coal-fired blast furnaces in power plants, where the flame retardant effect gradually diminishes, ensuring complete combustion within the blast furnace and preserving energy utilization. This composite material achieves efficient oxygen-barrier flame retardancy at room temperature and catalytic oxidation at high temperature, inhibiting oil-phase carbonization and coking, and improving burnout rate and clean combustion performance. It combines multiple advantages, including room-temperature flame retardancy, high-temperature combustion enhancement, and no residual carbon pollution, meeting the combined requirements of safe coal storage and transportation as well as efficient combustion utilization. It is suitable for safe coal utilization in various scenarios, including open-pit coal storage, long-distance coal transportation, and coal-fired power plants, demonstrating good engineering adaptability and promising application prospects. Attached Figure Description

[0026] Figure 1 The graph shows the change in CO release from the coal sample after treatment with the composite material prepared in Example 1 and the original coal.

[0027] Figure 2 The graph shows the heat release rate of the coal sample after composite material treatment and that of the raw coal prepared in Example 1.

[0028] Figure 3 The graph shows the change curves of elastic modulus of the composite materials prepared in Examples 1-3 at different shear rates. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Example 1

[0031] A method for preparing a high-temperature responsive composite material for synergistic regulation of flame retardancy and calorific value release in coal piles includes the following steps:

[0032] a. Weigh 12g of SiO2 and add it to 250ml of anhydrous ethanol for ultrasonic dispersion. Add 12g of polyethylene glycol and stir the mixture at 45℃ for 2 hours. After the reaction is complete, wash the mixture three times with deionized water and dry it in a vacuum drying oven at 80℃ for 6 hours to obtain organically modified SiO2 particles.

[0033] b. Dissolve 10g Mn(NO3)2·4H2O and 20g Fe(NO3)3·9H2O in 150ml deionized water, slowly add 25% ammonia water to control the pH at around 10.5, stir and react at 70℃ for 1.5 hours until MnFe2O4 nanoparticles are fully formed and precipitated, then add 1g polyvinyl alcohol and 7g isophorone diisocyanate to the reaction system, and react at 55℃ for 2 hours under nitrogen protection to obtain MnFe2O4 nanoparticles with hydroxyl functional groups grafted on the surface;

[0034] c. Add 70g of polypropylene glycol and 25g of polydimethylsiloxane (PDMS) to a 500ml reactor in a certain proportion, heat and stir at 65℃ for 30 minutes to form a homogeneous oil phase base system; slowly add 10ml of deionized water to adjust the viscosity and preliminary emulsification properties of the system; then slowly add 5g of pharmaceutical grade mineral oil, and continue stirring at 65℃ for 30 minutes to form a stable composite high calorific value carrier;

[0035] d. Add 3g of hydroquinone dihydroxyethyl ether to the composite high calorific value carrier obtained in step c, and stir the reaction at 70°C for 1.5 hours; during the reaction, ensure that the system is uniform and transparent to promote the formation of physical entanglement or chemical bridging structure between the aromatic ether linker and the polyether and PDMS;

[0036] e. Add 12g of organically modified SiO2 particles prepared in step a and 12g of MnFe2O4 nanoparticles grafted with hydroxyl functional groups prepared in step b to the mixture obtained in step d, and treat it at 70℃ for 1.5 hours at 3500r / min using a high-shear emulsifier to obtain a high-temperature responsive composite material for synergistic regulation of flame retardancy and calorific value release in coal piles.

[0037] Example 2

[0038] The preparation method of this embodiment differs from that of Example 1 in that: in step a, the mass of SiO2 and polyethylene glycol are 18g and 9g, respectively; in step b, the mass of Mn(NO3)2·4H2O, Fe(NO3)3·9H2O, polyvinyl alcohol, and isophorone diisocyanate are 8g, 20g, 0.8g, and 6.4g, respectively; in step c, the mass of polypropylene glycol, polydimethylsiloxane, and pharmaceutical-grade mineral oil are 65g, 20g, and 15g, respectively; and in step e, the mass of organically modified SiO2 particles and hydroxyl-grafted MnFe2O4 nanoparticles are 18g and 12g, respectively. The remaining processes and parameters are consistent with those of Example 1.

[0039] Example 3

[0040] The preparation method of this embodiment differs from that of Example 1 in that: in step a, the mass of SiO2 and polyethylene glycol are 8g and 16g, respectively; in step b, the mass of Mn(NO3)2·4H2O, Fe(NO3)3·9H2O, polyvinyl alcohol, and isophorone diisocyanate are 12g, 18g, 1.2g, and 6g, respectively; in step c, the mass of polypropylene glycol, polydimethylsiloxane, and pharmaceutical-grade mineral oil are 75g, 30g, and 10g, respectively; and in step e, the mass of organically modified SiO2 particles and hydroxyl-grafted MnFe2O4 nanoparticles are 9.2g and 16.1g, respectively. The remaining processes and parameters are consistent with those of Example 1.

[0041] 100g of coal sample with a particle size of 0.18-0.25mm was selected, vacuum dried at 60℃ for 4 hours, and divided into two equal parts. One part was mixed with the composite material prepared in Example 1 at a ratio of 8% of the coal sample mass to prepare two sets of samples: raw coal and treated coal sample, which were used for experimental testing in subsequent examples.

[0042] Two groups of coal samples were separately placed in a programmed temperature-increasing furnace with a heating rate of 3℃ / min. Air was introduced at a rate of 80 ml / min, and the CO concentration was analyzed using gas chromatography to calculate the CO release rate. Each sample was tested three times, and the average value was taken as the final result. The test results are as follows: Figure 1 As shown, below 140℃, the CO release of the raw coal sample begins to increase rapidly at around 100℃, while the CO release of the coal sample treated with the composite material remains at a low level at 140℃. This is because the organically modified SiO2 particles in the composite material form a physical barrier layer on the coal surface, significantly delaying the diffusion of oxygen into the coal matrix, inhibiting the initiation of the low-temperature oxidation chain reaction, and greatly postponing the temperature node for CO generation, demonstrating excellent low-temperature flame retardant potential. In the range of 140-240℃, the CO release of both types of coal samples gradually increases, but the CO release of the coal sample treated with the composite material is always significantly lower than that of the raw coal sample. In this stage, the MnFe2O4 nanoparticles in the composite material play a dual role: on the one hand, the hydroxyl functional groups grafted on their surface can adsorb some of the active free radicals generated by coal oxidation, interrupting the oxidation chain transmission; on the other hand, the physical barrier layer continuously weakens the oxygen supply, jointly limiting the degree of reaction between the active components in the coal and oxygen, effectively curbing the large-scale generation of CO. In the range of 240℃-300℃, the CO release of the treated coal sample is still much smaller than that of the raw coal, but the gap gradually narrows. This is because the composite material itself undergoes structural changes under high temperature conditions, which weakens its inhibitory effect on oxygen diffusion and oxidation reaction. Furthermore, MnFe2O4 nanoparticles gradually exhibit a catalytic tendency for complete coal oxidation at high temperatures, creating conditions for complete oxidation of coal and reducing pollutant residues in controlled combustion scenarios, thus achieving functional adaptation of strong flame retardancy at room temperature and synergistic regulation of combustion at high temperature.

[0043] Experimental data show that the composite material can effectively suppress the release of CO from coal at room temperature oxidation. At the same time, the suppression effect gradually decreases as the temperature increases, creating conditions for complete oxidation in the subsequent combustion process, thus achieving synergistic regulation of coal pile flame retardancy and subsequent combustion performance.

[0044] Two groups of coal samples were analyzed using a cone calorimeter at a radiation flux of 45 kW / m². 2 The calorific value was tested under the conditions of air flow rate of 24 L / min and humidity of 50% RH. The test results are as follows: Figure 2 As shown, in the initial stage of combustion (0-50s) at high temperatures, the heat release rate of the raw coal sample slowly increases in the initial stage because the reaction between the flammable components in the coal and oxygen requires a certain amount of time to accumulate heat. However, in the treated coal sample, the MnFe2O4 nanoparticles in the composite material have good catalytic activity, which can accelerate the reaction between the active groups on the coal surface and oxygen under thermal radiation. At the same time, the mixing of high-calorific-value fluids also makes the peak value of the treated coal sample higher than that of the raw coal. After the peak value, the heat release rate of the raw coal sample gradually decreases and fluctuates due to the rapid consumption of local flammable components and the certain obstruction of oxygen diffusion by gases such as CO2 produced during combustion, resulting in poor combustion stability. As the temperature rises, the catalytic effect of MnFe2O4 nanoparticles continues to be enhanced, promoting the reaction between the non-flammable components in the coal and oxygen. At the same time, the components of the composite material (such as polyether, PDMS, etc.) can participate in the reaction to supplement heat during combustion, and their uniform dispersion ensures continuous and stable oxygen penetration, causing the heat release rate to decline steadily. In the later stages of combustion of raw coal samples, the number of reactive components decreases significantly, the heat release rate continues to decline, and the combustion intensity weakens markedly. Thanks to the catalytic enhancement and heat replenishment of the coal combustion process by the composite material, recalcitrant components such as fixed carbon in the treated coal sample continue to participate in the reaction under the action of the catalyst. Simultaneously, the continuous energy release of the high-calorific-value carrier components in the material results in a stable heat release rate and an effectively extended exothermic cycle, improving the energy utilization rate of the fuel in the combustion system. In scenarios such as industrial boilers and clean coal utilization, it can achieve synergistic optimization of rapid ignition, efficient energy release, and stable operating conditions, demonstrating significant application value in industrial combustion scenarios requiring rapid heating and stable heat release.

[0045] The elastic modulus of the composite materials prepared in Examples 1-3 were measured at different shear rates using a rotational rheometer equipped with a parallel plate measurement system. Before testing, the samples were placed in a constant temperature environment of 25℃ for 1 hour to eliminate the influence of thermal history. During the test, the temperature was controlled at 25℃±0.1℃, and the shear rate range was set to 0.1-1000s. -1 By using dynamic frequency scanning and steady-state shear testing, elastic modulus data at different shear rates were obtained. The experimental results are as follows: Figure 3As shown, in Example 2, the increased SiO2 content resulted in more inorganic particles forming a dense network support in the oil phase system. Simultaneously, the synergistic effect between the MnFe2O4 surface grafting system and the oil phase binder was more pronounced, strengthening the system's cohesion. Therefore, the shear viscosity was the highest at all shear rates, demonstrating superior deformation resistance. In Example 3, the reduced SiO2 content and increased PDMS ratio resulted in a sparser inorganic particle network, enhancing the dominance of oil phase fluidity. With increasing shear rate, the system viscosity decreased rapidly, exhibiting the largest decrease in shear viscosity and the most prominent shear thinning characteristic, making it suitable for scenarios with extremely high fluidity requirements. Example 1, with its balanced formulation parameters, achieved a shear viscosity between that of Examples 2 and 3, striking a balance between shape retention and shear dispersion, thus meeting the needs of conventional coal pile treatment construction.

[0046] The composite materials prepared in the above embodiments all exhibit pseudoplastic fluid characteristics, with shear viscosity decreasing as shear rate increases. At low shear rates, the network structure formed by the physical entanglement and chemical grafting of organically modified SiO2 particles, MnFe2O4 nanoparticles, and the oil phase system within the material remains stable, exhibiting a high elastic modulus and maintaining shape stability. At high shear rates, shear force disrupts the network structure, enhancing system fluidity and significantly reducing the elastic modulus, which is beneficial for dispersion operations in engineering applications such as pumping and spraying.

Claims

1. A high-temperature responsive composite material for synergistic regulation of flame retardancy and calorific value release in coal piles, characterized in that, The material is synergistically composed of a mixed system of organically modified inorganic particulate fillers, a composite high-calorific-value carrier, and an aromatic ether linker. The organically modified inorganic particulate fillers include organically modified SiO2 particles and MnFe2O4 nanoparticles grafted with hydroxyl functional groups. The composite high-calorific-value carrier is composed of a mixture of polyether, polydimethylsiloxane, and a white oil-based high-calorific-value oil phase in a specific ratio. The aromatic ether linker is hydroquinone dihydroxyethyl ether or resorcinol-bis(β-hydroxyethyl) ether. The organically modified SiO2 particles and the MnFe2O4 nanoparticles grafted with hydroxyl functional groups account for 6-20% and 10-15% of the mass of the mixed system, respectively. The modification method of the organic modified SiO2 particles is as follows: SiO2 is added to anhydrous ethanol and ultrasonically dispersed, polyethylene glycol is added, and the mixture is stirred and reacted at 40-50℃. After washing and drying with deionized water, the particles are obtained. The modification method of grafted MnFe2O4 nanoparticles with hydroxyl functional groups is as follows: Mn(NO3)2·4H2O and Fe(NO3)3·9H2O are dissolved in deionized water, the pH is controlled at 10-11, and the reaction is stirred at 70°C until MnFe2O4 nanoparticles are fully formed and precipitated. Then, polyvinyl alcohol and isophorone diisocyanate are added to the reaction system, and the reaction is carried out at 50-60°C under nitrogen protection.

2. A method for preparing a high-temperature responsive composite material for synergistic regulation of flame retardancy and calorific value release in coal piles as described in claim 1, characterized in that, Includes the following steps: a. Add SiO2 to anhydrous ethanol and disperse it by ultrasonication. Add polyethylene glycol and stir the reaction at 40-50℃. Then wash and dry with deionized water to obtain organically modified SiO2 particles. b. Dissolve Mn(NO3)2·4H2O and Fe(NO3)3·9H2O in deionized water, control the pH at 10-11, and stir the reaction at 70°C until MnFe2O4 nanoparticles are fully formed and precipitated. Then, add polyvinyl alcohol and isophorone diisocyanate to the reaction system and react at 50-60°C under nitrogen protection to obtain MnFe2O4 nanoparticles with hydroxyl functional groups grafted on the surface. c. Add polyether and polydimethylsiloxane to a reaction vessel in a certain proportion, and heat and stir at 60-70°C to form a homogeneous oil phase base system; add an appropriate amount of deionized water to the homogeneous oil phase base system, and then add white oil-based high calorific value oil phase, and continue stirring at the same temperature to form a stable composite high calorific value carrier; d. Add an aromatic ether linker to the composite high-calorific-value carrier obtained in step c, and stir the reaction at 60-75°C for 1-2 hours to obtain a mixed system; the aromatic ether linker is hydroquinone dihydroxyethyl ether or resorcinol-bis(β-hydroxyethyl) ether; e. The organically modified SiO2 particles prepared in step a and the MnFe2O4 nanoparticles grafted with hydroxyl functional groups prepared in step b are added to the mixture obtained in step d in proportion. The mixture is emulsified at 60-75℃ for 1-2 hours under stirring to obtain a high-temperature responsive composite material for synergistic regulation of flame retardancy and calorific value release in coal piles. The organically modified SiO2 particles and the MnFe2O4 nanoparticles grafted with hydroxyl functional groups account for 6-20% and 10-15% of the mass of the mixture, respectively.

3. The method for preparing a high-temperature responsive composite material for synergistic regulation of flame retardancy and calorific value release in coal piles according to claim 2, characterized in that, In step a, the mass ratio of SiO2 to polyethylene glycol is (0.5-2):1; the reaction is stirred for 2 hours; the mass-to-volume ratio of SiO2 to anhydrous ethanol is 1 g: (13-32) ml.

4. A method for preparing a high-temperature responsive composite material for synergistic regulation of flame retardancy and calorific value release in coal piles, as described in claim 2 or 3, characterized in that, In step b, the mass ratio of Mn(NO3)2·4H2O to Fe(NO3)3·9H2O is 1:(1.5-2.5); the reaction is stirred for 1.5 h; the mass-volume ratio of Mn(NO3)2·4H2O to deionized water is 1 g:(12-19) ml.

5. A method for preparing a high-temperature responsive composite material for synergistic regulation of flame retardancy and calorific value release in coal piles, as described in claim 2 or 3, characterized in that, In step b, the mass ratio of Mn(NO3)2·4H2O, polyvinyl alcohol, and isophorone diisocyanate is 10:1:(5-10); the reaction is carried out under nitrogen protection for 2 hours.

6. A method for preparing a high-temperature responsive composite material for synergistic regulation of flame retardancy and calorific value release in coal piles, as described in claim 2 or 3, characterized in that, In step c, the polyether is selected from polypropylene glycol or polyethylene glycol; the white oil high-calorific-value oil phase is pharmaceutical-grade mineral oil or light paraffin oil.

7. A method for preparing a high-temperature responsive composite material for synergistic regulation of flame retardancy and calorific value release in coal piles, as described in claim 2 or 3, characterized in that, In step c, the mass ratio of polyether, polydimethylsiloxane and white oil-based high-calorific-value oil phase in the composite high-calorific-value carrier is (4-14):(1-5):

1.

8. A method for preparing a high-temperature responsive composite material for synergistic regulation of flame retardancy and calorific value release in coal piles, as described in claim 2 or 3, characterized in that, In step d, the aromatic ether linker accounts for 2.4-2.8% of the mass fraction of the composite high calorific value carrier.

9. The application of a composite material as described in claim 1 or a composite material prepared by any one of the preparation methods described in claims 2-8 in the flame retardancy of coal piles, wherein the composite material is sprayed to cover the surface of coal particles to form a hydrophobic oxygen barrier, or injected into the cracks of the coal pile by pressurized injection to seep in and seal the air leakage channels and replace the free oxygen inside the pile.

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