Anti-oxidation temperature-shock microcapsule inhibitor for inhibiting spontaneous combustion of coal and preparation method of anti-oxidation temperature-shock microcapsule inhibitor

Abstract

The invention discloses an antioxidant temperature shock microcapsule inhibitor for inhibiting coal spontaneous combustion and a preparation method thereof, and belongs to the technical field of coal spontaneous combustion disaster prevention and control. According to the preparation method, tea polyphenol is taken as a core material, polyethylene glycol and sodium bicarbonate are taken as wall materials, and the antioxidant temperature shock microcapsule inhibitor with the coating rate of 85% is obtained through microcapsule assembly; wherein the solution ratio of the core material to the wall material is 1: 3; the solution ratio of polyethylene glycol to sodium bicarbonate is 7: 3; the parameters in the microcapsule assembling process are as follows: the injection speed is 2mL / min, and the stirring speed is 800r / min. According to the invention, a'temperature response type organic-inorganic hybrid wall material-antioxidant core material 'microcapsule system is constructed to form a'physical isolation-chemical inhibition-inert gas protection' triple inhibition mechanism, so that the inhibition rate of a coal sample at about 90 DEG C can reach 87.5% under the condition that the addition amount is 10%; the technical problems that a traditional inhibitor is low in coating rate, inaccurate in temperature response, insufficient in inhibition efficiency and the like are effectively solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal spontaneous combustion disaster prevention and control, and in particular relates to an antioxidant temperature-induced microcapsule inhibitor for inhibiting coal spontaneous combustion and a preparation method thereof. Background Art

[0002] Coal occupies a dominant position in the energy structure, and coal spontaneous combustion is one of the five most common mine disasters. Inhibitors are a common means of preventing coal spontaneous combustion. Inhibitors work synergistically by absorbing heat, cooling, and isolating oxygen, as well as inhibiting or interrupting chain reactions, thereby delaying the oxidation reaction of coal and suppressing the occurrence of coal spontaneous combustion. Currently, there are three main types of inhibitors commonly used: physical inhibitors, chemical inhibitors, and new composite inhibitors. Inhibitors are easy to use and have significant effects, but they also have limitations. For example, composite inhibitors are relatively expensive, and chemical inhibitors may pollute the environment. Therefore, the development of new inhibitors with high inhibition efficiency, long inhibition life, and strong targeting is the current research direction of coal spontaneous combustion inhibition technology.

[0003] Microencapsulation technology, as an advanced coating technique, preserves the original chemical properties of the core material. Its controlled-release mechanism relies on the selective permeability or controlled rupture of the wall material, enabling sustained and precise release of the core material. This technology offers four key advantages: enhancing core material stability, regulating its physical properties, enabling controlled release, and isolating the active ingredient. Due to its outstanding high efficiency and long-lasting effectiveness, microencapsulation technology presents broad application prospects in the controlled-release field. Antioxidants offer high inhibitory efficiency, are environmentally friendly, efficient, and widely available. However, due to high humidity, high temperatures, and fluctuating ambient conditions, antioxidants can easily lose their activity and struggle to maintain their inhibitory effect. Therefore, microencapsulation technology is needed to encapsulate antioxidants and improve their inhibitory efficiency. Currently, the application of microencapsulation wall materials in coal spontaneous combustion inhibition projects still faces significant limitations: 1) While single organic polymers offer high encapsulation rates, they suffer from poor thermal stability and are prone to decomposition and failure in the high temperatures of the coal pile; 2) Inorganic materials, while heat-resistant, are brittle and prone to rupture, leading to premature leakage of the inhibitor. These problems directly affect the long-term fire prevention and extinguishing effect of microcapsule inhibitors in coal mines.

[0004] In view of this situation, the development of organic-inorganic composite capsule shell materials has significant engineering value. In the future, it is necessary to focus on breakthroughs in low-cost large-scale preparation processes, and change the molecular weight of the wall material in combination with the coal quality characteristics of different mining areas to achieve different release temperatures, so as to meet the multiple requirements of coal mine 10,000-ton coal pile retardation projects for material intelligence, reliability and economy. Summary of the Invention

[0005] To this end, the present invention proposes an antioxidant temperature-activated microcapsule inhibitor for inhibiting coal spontaneous combustion and a preparation method thereof.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] One of the objectives of the present invention is to provide a method for preparing an antioxidant-type temperature-activated microcapsule inhibitor for inhibiting coal spontaneous combustion, wherein tea polyphenol (GTP) is used as a core material, polyethylene glycol (PEG) and sodium bicarbonate are used as wall materials, and an antioxidant-type temperature-activated microcapsule inhibitor with a coverage rate of 85% is obtained by microcapsule assembly;

[0008] The volume ratio of the core material to the wall material is 1:3. The core material and the wall material here refer to their corresponding solutions, that is, the core material is tea polyphenol solution, and the wall material is PEG-NaHCO3 prepolymer.

[0009] The volume ratio of polyethylene glycol to sodium bicarbonate is 7:3, where the ratio refers to the ratio of the corresponding solutions of polyethylene glycol and sodium bicarbonate, i.e., polyethylene glycol refers to molten polyethylene glycol, and sodium bicarbonate refers to a sodium bicarbonate solution;

[0010] The parameters during the microcapsule assembly process were: injection speed of 2 mL / min and stirring speed of 800 r / min.

[0011] This invention designs an antioxidant, temperature-activated microcapsule inhibitor specifically designed to prevent spontaneous combustion during coal stacking. A key feature of these microcapsules is their ability to "sense" temperature changes: when the coal pile's temperature rises to a dangerous level, the microcapsule wall material melts and releases the inhibitor core, effectively acting at the critical moment when the coal is about to spontaneously combust. Tea polyphenols are used as the microcapsule core material, while polyethylene glycol and sodium bicarbonate are used as the wall materials. These materials are not only inexpensive, safe, and non-toxic, but more importantly, they are able to actively respond to temperature changes. Tea polyphenols, as natural antioxidants, effectively capture free radicals, effectively blocking the chain reaction of coal oxidation. Polyethylene glycol acts as a temperature switch, melting at a specific temperature, while sodium bicarbonate absorbs heat when heated. The combined protective shell of these two materials effectively encapsulates the antioxidant and releases it when needed. Simply spreading these microcapsules on the surface of a coal pile monitors the temperature around the clock, automatically triggering a protective mechanism before danger strikes, making them more precise and efficient than traditional manual spraying methods.

[0012] Furthermore, the method specifically comprises the following steps:

[0013] Adding tea polyphenol powder to deionized water and stirring at a constant temperature to obtain a tea polyphenol solution;

[0014] Pour the sodium bicarbonate solution into molten polyethylene glycol and stir at constant temperature to obtain PEG-NaHCO3 prepolymer;

[0015] Using a syringe pump, mixing the prepolymer and the tea polyphenol solution while stirring to obtain a mixed solution;

[0016] The mixed solution is solidified and dried, ground and sieved to obtain an antioxidant temperature-activated microcapsule inhibitor.

[0017] Furthermore, the conditions for preparing the tea polyphenol solution are: stirring in a water bath at 60° C. and 800 rpm for 1 hour.

[0018] Furthermore, the specific preparation step of the molten polyethylene glycol includes: heating the polyethylene glycol in a constant temperature water bath at 70° C. to a molten state.

[0019] Furthermore, the conditions for preparing the PEG-NaHCO3 prepolymer are: stirring in a water bath at 60°C and 800 r / min for 1 hour.

[0020] Furthermore, the injection speed of the injection pump during use is 2 mL / min, and the stirring speed is controlled at 800 r / min to form a stable emulsified system.

[0021] Furthermore, the specific operation steps of the curing and drying are: transferring the mixed solution to a constant temperature water bath at 55°C, maintaining a stirring speed of 800 r / min to continue the reaction for 20-24 hours to complete the curing, and then placing it in a 45°C forced air drying oven to dry for 12 hours.

[0022] Furthermore, the grinding and screening refers to passing through a 200-mesh sieve after grinding.

[0023] The second object of the present invention is to provide an antioxidant temperature-activated microcapsule inhibitor prepared by the above preparation method.

[0024] The third object of the present invention is to provide an antioxidant temperature-activated microcapsule inhibitor for use in the field of preventing and controlling coal spontaneous combustion disasters.

[0025] Furthermore, the addition amount of the antioxidant temperature-induced microcapsule inhibitor is 4-19% of the mass of the coal sample, such as 4%, 7%, 10%, 13%, 16% and 19%, preferably 10%.

[0026] Compared with the prior art, the present invention has the following advantages and technical effects:

[0027] The present invention achieves intelligent controlled release of the inhibitor by constructing a microcapsule system of "temperature-responsive organic-inorganic hybrid wall material-antioxidant core material", utilizing the synergistic effect of the temperature-sensitive phase change characteristics of PEG6000 and the thermal decomposition characteristics of NaHCO3, combined with an optimized core-to-wall ratio structural design. Specifically, when the ambient temperature reaches the critical temperature of coal spontaneous combustion (60-80°C), PEG6000 melts and destroys the capsule wall structure, while NaHCO3 decomposes under heat to release CO2 and absorb heat. The synergistic effect of the two promotes the rapid release of tea polyphenols: on the one hand, the liquid film formed by the melting of PEG can cover the surface of the coal body to isolate oxygen; on the other hand, the CO2 produced by the decomposition of NaHCO3 dilutes the oxygen concentration, and combined with the antioxidant effect of tea polyphenols, forms a triple inhibition mechanism of "physical isolation-chemical inhibition-inert gas protection". This design enables the microcapsule coverage rate to reach over 85%, and the temperature response deviation is less than ±2°C. At a 10% addition amount, the coal sample's inhibition rate can reach 87.5% at around 90°C, effectively solving the technical problems of traditional inhibitors such as low coverage rate, inaccurate temperature response, and insufficient inhibition efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 This is a flow chart for preparing the antioxidant temperature-stimulated microcapsules according to Example 1 of the present invention;

[0030] Figure 2 The oxygen consumption rate of coal spontaneous combustion under different addition amounts of antioxidant temperature-induced microcapsule inhibitors; A1 is the raw coal; B1-B6 are inhibitory coal samples with different addition amounts (4%, 7%, 10%, 13%, 16% and 19%); the small figure is an enlarged view at 30-90℃;

[0031] Figure 3 The CO release rate of coal spontaneous combustion at different addition levels of antioxidant temperature-induced microcapsule inhibitors; A1 is the raw coal; B1-B6 are inhibitory coal samples with different addition levels (4%, 7%, 10%, 13%, 16% and 19%); the small figure is an enlarged view at 30-90°C;

[0032] Figure 4 The CO2 release rate under different addition amounts of antioxidant temperature-induced microcapsule inhibitors; A1 is the raw coal; B1-B6 are inhibitory coal samples with different addition amounts (4%, 7%, 10%, 13%, 16% and 19%); the small figure is an enlarged view at 30-90℃;

[0033] Figure 5The spontaneous combustion inhibition rate of coal at different addition amounts of antioxidant temperature-induced microcapsule inhibitors; B1-B6 are inhibitory coal samples with different addition amounts (4%, 7%, 10%, 13%, 16% and 19%) respectively; the small figure is an enlarged view at 30-90℃;

[0034] Figure 6 The figure is a coverage curve of the antioxidant temperature-induced microcapsule inhibitor prepared at different core-to-wall ratios in Comparative Example 1;

[0035] Figure 7 This is the effect of the operating temperature of the anti-oxidation temperature-activated microcapsule inhibitor at different core-to-wall ratios in Comparative Example 1;

[0036] Figure 8 The figure is a curve of the coverage rate of the antioxidant temperature-induced microcapsule inhibitor prepared at different polyethylene glycol addition amounts in Comparative Example 2;

[0037] Figure 9 This is a graph showing the effect of different polyethylene glycol addition amounts on the operating temperature of the antioxidant temperature-activated microcapsule inhibitor in Comparative Example 2;

[0038] Figure 10 The figure is a coverage curve of the antioxidant temperature-induced microcapsule inhibitor prepared at different injection rates in Comparative Example 3;

[0039] Figure 11 This is a graph showing the effect of the operating temperature of the anti-oxidation temperature-activated microcapsule inhibitor at different injection rates in Comparative Example 3;

[0040] Figure 12 The figure is a coverage curve of the antioxidant temperature-induced microcapsule inhibitor prepared at different stirring speeds in Comparative Example 4;

[0041] Figure 13 This is a graph showing the effect of the operating temperature of the anti-oxidation temperature-activated microcapsule inhibitor at different stirring speeds in Comparative Example 4;

[0042] Figure 14 This is a characteristic diagram of the change in thermal diffusion coefficient of the original coal sample and the inhibitory coal sample due to different core materials in comparative example 5. DETAILED DESCRIPTION

[0043] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0044] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0045] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0046] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0047] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0048] The antioxidant temperature-stimulated microcapsule inhibitor provided by the present invention includes the following contents:

[0049] (1) Organic-inorganic wall material design: PEG6000 and NaHCO3 composite material combines the temperature sensitivity of PEG and the thermal stability of NaHCO3, overcoming the defects of traditional single wall material such as uneven coating or large temperature response deviation;

[0050] (2) Dynamic process control: By synergistically optimizing the injection speed (2 mL / min) and stirring speed (800 rpm), the microcapsule coverage rate was increased to 85%, ensuring uniform microcapsule particle size and a stable emulsification system;

[0051] (3) Multiple inhibition mechanisms: The core material (antioxidant) and the wall material (physical and chemical inhibition) work synergistically to trigger the triple effects of heat absorption, oxygen isolation, and gas dilution at the critical temperature, significantly improving the inhibition rate compared to a single inhibitor.

[0052] The present invention provides a method for preparing an antioxidant temperature-activated microcapsule inhibitor for inhibiting coal spontaneous combustion, which specifically includes the following steps:

[0053] 1) Preparation of tea polyphenol solution: Accurately weigh tea polyphenol powder and add it to deionized water preheated to 60°C. Stir continuously at 800 rpm in a constant temperature water bath for 1 hour to obtain a uniformly dispersed tea polyphenol solution.

[0054] 2) Preparation of molten polyethylene glycol: Weigh a certain amount of PEG6000 into a 500 mL beaker and heat in a 70°C water bath until completely molten. Then adjust the water bath temperature to 50°C and maintain this constant temperature until ready for use.

[0055] 3) Preparation of sodium bicarbonate solution: Weigh sodium bicarbonate powder and add it to deionized water. Stir continuously with a glass rod until completely dissolved to obtain a clear, transparent aqueous NaHCO3 solution. Slowly pour the prepared sodium bicarbonate solution into molten polyethylene glycol and stir continuously at 800 rpm in a 60°C water bath for 1 hour using a mechanical stirrer to form a uniform and stable PEG-NaHCO3 prepolymer. The volume ratio of molten polyethylene glycol to sodium bicarbonate solution is 7:3.

[0056] 4) Microcapsule assembly: Using a syringe pump, the PEG-NaHCO3 prepolymer and the tea polyphenol solution were slowly mixed in proportion at a constant flow rate of 2 mL / min while stirring at 800 r / min to form a stable emulsified system, i.e., a mixed solution; wherein the volume ratio of the tea polyphenol solution to the PEG-NaHCO3 prepolymer was 1:3;

[0057] 5) Curing and drying: Transfer the mixture to a 55°C constant temperature water bath, maintain a stirring speed of 800 rpm for 20-24 hours to complete the curing, and then place it in a 45°C forced air drying oven to dry for 12 hours;

[0058] 6) Post-processing step: Grind the dried product and sieve it through a 200-mesh standard sieve to finally obtain an antioxidant temperature-activated microcapsule powder product with uniform particle size, namely, an antioxidant temperature-activated microcapsule inhibitor.

[0059] In the preparation of the antioxidant temperature-stimulated microcapsule inhibitor, the present invention primarily considers the influence of four factors on the encapsulation efficiency and temperature sensitivity of the antioxidant temperature-stimulated microcapsules: the ratio of the microcapsule core material to the wall material, the ratio of the two wall materials, the injection speed of the programmable syringe pump, and the stirring speed of the electric stirrer. The parameter determination method and experimental design are as follows:

[0060] (1) Core-to-wall ratio:

[0061] In the preparation of microcapsules, the core-to-wall ratio refers to the mass ratio of the inhibitor core material to the wall material. This parameter has a decisive influence on the performance of the product: an appropriate core-to-wall ratio can ensure both sufficient inhibitor loading and a complete coating effect. Too high a ratio will lead to incomplete coating, while too low a ratio will cause material waste and affect the release efficiency of the inhibitor. The present invention uses ultraviolet spectrophotometry and thermogravimetric analysis to investigate the effects of different core-to-wall ratios on the performance of microcapsules. The experimental results show that when the volume ratio of the core material to the wall material is 1:3 (that is, the volume ratio of the tea polyphenol solution to the PEG-NaHCO3 prepolymer is 1:3), the microcapsules exhibit optimal performance, a high coating rate, and a thermal response temperature earlier than the critical temperature of coal spontaneous combustion. This ratio indicates that the intermolecular forces have reached the optimal balance.

[0062] (2) PEG6000 dosage:

[0063] In the microcapsule preparation process, the amount of PEG6000 added refers to its mass percentage in the wall material system. Because PEG6000 is an organic component, its content directly affects the viscosity and thermal response properties of the wall material solution: Properly increasing the viscosity can reduce the diffusion rate of core material molecules, reduce collision and aggregation, and thus improve the stability of the microcapsules. Furthermore, the phase change properties of PEG determine the thermosensitive release performance of the microcapsules. This study used viscometry and differential scanning calorimetry to evaluate the impact of the PEG6000 content on product performance. Experimental data showed that when the PEG6000 content reached 70%, the prepared microcapsules exhibited optimal overall performance, with the coverage rate increasing to 85%. This optimal ratio is achieved because the high PEG content creates a viscous system that effectively inhibits core material leakage. Furthermore, when molten polyethylene glycol and sodium bicarbonate solution are combined in a volume ratio of 7:3, the synergistic effect of the two forms an organic-inorganic hybrid wall material that retains the thermosensitive properties of PEG while retaining the thermal stability of inorganic salts.

[0064] (3) Injection speed:

[0065] During the microcapsule preparation process, the liquid injection speed refers to the flow rate when the core material and wall material solution are injected into the microfluidic device. The liquid injection speed directly affects the shear force during the microdroplet formation process, and thus determines the particle size distribution and coating effect of the microcapsules. Therefore, the present invention adopts a controlled variable method to evaluate the quality of microcapsules at different speeds by adjusting the injection speed, combining laser particle size analysis and scanning electron microscopy observation. Experimental data show that when the injection speed is 2mL / min, the shear force generated at this speed can ensure that the core material is fully dispersed and form microdroplets with uniform particle size. Too low a speed will lead to uneven dispersion, while too high a speed will cause droplet breakage, both of which will reduce the coating rate.

[0066] (4) Stirring speed:

[0067] In the microcapsule preparation process, the stirring speed refers to the rotation speed (r / min) of the mechanical stirring of the dispersed system. This parameter needs to be precisely controlled because it directly affects the magnitude of the shear stress in the system, which in turn determines the dispersion state of the droplets. The present invention investigates the effects of different stirring speeds on the performance of microcapsules through laser particle size analysis and scanning electron microscopy observation. Experimental data show that when the stirring speed is 800r / min, the prepared microcapsules have the best comprehensive performance. The shear stress generated by this rotation speed can effectively overcome the aggregation effect of surface tension and viscous stress to form microdroplets with uniform particle size; under this condition, the droplet formation and coating process reach a dynamic equilibrium. When the rotation speed is low, insufficient shear force will cause the droplets to coalesce; when the rotation speed is high, excessive shear force will destroy the integrity of the capsule wall, resulting in an increase in the proportion of hollow capsules.

[0068] When preparing antioxidant microcapsules, the selection of preparation parameters should consider both the microcapsule coverage efficiency and the operating temperature requirements. A comprehensive analysis of these four parameters, conducted through single-factor experiments and response surface regression analysis of the microcapsule operating temperature, revealed that the key parameters for preparing antioxidant temperature-induced microcapsules are a PEG6000 dosage of 70% (i.e., a 7:3 volume ratio of molten polyethylene glycol to sodium bicarbonate solution), a core material to wall material volume ratio of 1:3, an injection speed of 2 mL / min, and a stirring speed of 800 rpm. Under these conditions, the theoretical coverage efficiency is 85% and the operating temperature is approximately 73.6°C.

[0069] The raw materials used in the present invention are all purchased from the market.

[0070] The technical solution of the present invention is further illustrated by the following examples.

[0071] Example 1

[0072] like Figure 1 As shown, a method for preparing an antioxidant temperature-activated microcapsule inhibitor for inhibiting coal spontaneous combustion specifically comprises the following steps:

[0073] 1) Preparation of tea polyphenol solution: Accurately weigh 12.5 g of tea polyphenol powder and add it to 500 mL of deionized water preheated at 60°C. Stir continuously in a constant temperature water bath at 800 rpm for 1 h to prepare a uniformly dispersed tea polyphenol solution (GTP solution).

[0074] 2) Preparation of molten polyethylene glycol: Weigh 26.25 g of PEG6000 into a 500 mL beaker and heat in a 70°C water bath until completely molten. Then adjust the water bath temperature to 50°C and maintain this constant temperature until ready for use.

[0075] 3) Preparation of sodium bicarbonate solution: Weigh 11.25 g of sodium bicarbonate powder and add it to 500 mL of deionized water. Stir continuously with a glass rod until completely dissolved to obtain a clear, transparent NaHCO3 aqueous solution.

[0076] 4) Slowly pouring the sodium bicarbonate solution into the molten polyethylene glycol in a volume ratio of 7:3, stirring continuously at 800 rpm in a 60°C water bath for 1 hour using a mechanical stirrer to form a uniform and stable PEG-NaHCO3 prepolymer;

[0077] 5) Microcapsule assembly: Using a syringe pump, the PEG-NaHCO3 prepolymer and the tea polyphenol solution were slowly mixed in proportion at a constant flow rate of 2 mL / min while stirring at 800 r / min to obtain a mixed solution; wherein the volume ratio of the tea polyphenol solution to the PEG-NaHCO3 prepolymer was 1:3;

[0078] 6) Curing and drying: The mixture was transferred to a 55°C constant temperature water bath and stirred at 800 rpm for 24 hours to complete the curing. The mixture was then dried in a 45°C forced air drying oven for 12 hours.

[0079] 7) Post-processing step: The dried product is ground and sieved through a 200-mesh standard sieve to finally obtain an antioxidant temperature-activated microcapsule powder product with uniform particle size, that is, an antioxidant temperature-activated microcapsule inhibitor with a coverage rate of 85%.

[0080] Application Example 1

[0081] The antioxidant temperature-activated microcapsule inhibitor prepared in Example 1 was added to coal samples to test the effect of inhibiting coal spontaneous combustion. The addition amounts of the antioxidant temperature-activated microcapsule inhibitor were 4%, 7%, 10%, 13%, 16% and 19% of the coal sample mass, respectively.

[0082] Performance Testing

[0083] 1. Oxygen consumption rate of coal spontaneous combustion

[0084] A programmed temperature experiment was carried out on the coal samples with different addition amounts mentioned above to analyze the oxygen consumption rate of coal spontaneous combustion.

[0085] Figure 2The oxygen consumption rate of coal spontaneous combustion at different addition amounts of antioxidant temperature-induced microcapsules can be seen. It can be seen that after adding antioxidant microcapsules, the oxygen consumption rate of the coal sample is significantly reduced and remains at a low level at around 90°C. The turning point of oxidation acceleration is delayed by about 20°C compared with the original coal. As the addition amount of microcapsules increases, the inhibition effect first increases and then weakens. The inhibition effect is best when the addition amount is 10%: the oxygen consumption rate at around 90°C is reduced by 57.1% compared with the original coal, and is reduced by 339.6×10 -11 mol·cm -3 ·s -1 This is because excessive addition will cause the capsule wall material to aggregate, reduce the thermal melting efficiency, delay the release of the core material, and weaken the retardation effect.

[0086] 2. CO and CO2 release rates from coal spontaneous combustion

[0087] The CO and CO2 release rates during spontaneous combustion of coal samples with different addition amounts were analyzed to determine whether the addition of antioxidant microcapsules can effectively inhibit the release of CO and CO2 during coal oxidation.

[0088] Figure 3 、 Figure 4 Figures 2 and 3 show the CO and CO₂ release rates during coal spontaneous combustion at different addition levels of the antioxidant temperature-activated microcapsule inhibitor. It can be seen that the characteristic gas release rates of all the inhibited coal samples were significantly lower than those of the original coal, with a 10% addition demonstrating the optimal inhibitory effect: at around 90°C, the CO release rate was only 43.2% of that of the original coal, and the CO₂ release rate was 49.4% lower than that of the original coal. The inhibitory effect indicates that 10% is the optimal addition concentration, while higher addition levels can lead to decreased inhibitory efficiency due to aggregation of the capsule wall material. These results confirm that the appropriate addition of antioxidant microcapsules can significantly slow the oxidation process of coal.

[0089] 3. Coal spontaneous combustion resistance rate

[0090] The coal spontaneous combustion resistance rate of the coal samples with different addition amounts was analyzed.

[0091] Figure 5The figure shows the spontaneous combustion inhibition rate of coal at different addition levels of antioxidant temperature-induced microcapsule inhibitors. It can be seen that the inhibition effect of coal samples treated with different addition levels of antioxidant microcapsules shows a trend of first increasing and then decreasing. The inhibition rate increases most significantly in the temperature range of 60-80°C. This is mainly due to the thermal decomposition of the microcapsule wall material PEG-NaHCO3 at the critical temperature point of around 70°C: on the one hand, it lowers the ambient temperature by absorbing heat, and on the other hand, the decomposition products form a protective layer that isolates oxygen. The released CO2 and water vapor further dilute the oxygen concentration, thereby significantly delaying the spontaneous combustion process of coal. Experimental data shows that the inhibition effect is the best at a 10% addition level, reaching a maximum inhibition rate of 87.5% at around 90°C. The ranking of the inhibition effects of the samples shows that 10% is the optimal addition concentration. This result is consistent with the conclusions of the aforementioned tests on oxygen consumption rate and characteristic gas release rate, once again confirming that 10% is the optimal addition concentration.

[0092] Comparative Example 1

[0093] Same as Example 1, except that, in step 5), the volume ratios of the tea polyphenol solution and the PEG-NaHCO3 prepolymer are adjusted to 1:1, 1:2, 1:3, 1:4, and 1:5, respectively.

[0094] Figure 6 The figure is a coverage curve of the antioxidant temperature-induced microcapsule inhibitor prepared at different core-to-wall ratios in Comparative Example 1;

[0095] Figure 7 This is the effect of the operating temperature of the anti-oxidation temperature-activated microcapsule inhibitor at different core-to-wall ratios in Comparative Example 1;

[0096] from Figure 6 and Figure 7 It can be seen from the figure that with the decrease of the core-to-wall ratio, the coverage first increases and then decreases, among which the coverage rate reaches the best of 85% when the core-to-wall ratio is 1:3; with the decrease of the core-to-wall ratio, the operating temperature of the microcapsules fluctuates.

[0097] Comparative Example 2

[0098] The same as Example 1, except that, in step 4), the volume ratios of molten polyethylene glycol and sodium bicarbonate solution are adjusted to 54:46, 58:42, 62:38, 66:34, and 70:30, respectively, that is, the volume proportions of molten polyethylene glycol are 54%, 58%, 62%, 66%, and 70%, respectively.

[0099] Figure 8 The figure is a curve of the coverage rate of the antioxidant temperature-induced microcapsule inhibitor prepared at different polyethylene glycol addition amounts in Comparative Example 2;

[0100] Figure 9The graph of the effect of the action temperature of the antioxidant temperature-activated microcapsule inhibitor under different polyethylene glycol addition amounts in Comparative Example 2; Figure 8 and Figure 9 It can be seen that with the increase of PEG usage, the coverage rate shows a trend of first decreasing and then increasing, while the operating temperature fluctuates. When the PEG addition amount is 70%, the microcapsule operating temperature is 73.6℃, and the coverage rate reaches the best at 85%.

[0101] Comparative Example 3

[0102] Same as Example 1, except that, in step 5), the injection speed of the syringe pump is adjusted to 1 mL / min, 1.5 mL / min, 2 mL / min, 2.5 mL / min, and 3 mL / min, respectively.

[0103] Figure 10 The figure is a coverage curve of the antioxidant temperature-induced microcapsule inhibitor prepared at different injection rates in Comparative Example 3;

[0104] Figure 11 This is a graph showing the effect of the operating temperature of the anti-oxidation temperature-activated microcapsule inhibitor at different injection rates in Comparative Example 3;

[0105] from Figure 10 and Figure 11 It can be seen that with the gradual increase of liquid injection speed, the coverage rate shows a trend of first increasing and then decreasing, and the action temperature shows a trend of first decreasing and then increasing; when the injection speed is 2mL / min, the action temperature of the microcapsules prepared can meet the basic requirement of releasing the core material inhibitor before the critical temperature of coal spontaneous combustion.

[0106] Comparative Example 4

[0107] Same as Example 1, except that, in step 5), the stirring speed is adjusted to 400 r / min, 600 r / min, 800 / min, 1000 r / min, and 1200 r / min.

[0108] Figure 12 The figure is a coverage curve of the antioxidant temperature-induced microcapsule inhibitor prepared at different stirring speeds in Comparative Example 4;

[0109] Figure 13 This is a graph showing the effect of the operating temperature of the anti-oxidation temperature-activated microcapsule inhibitor at different stirring speeds in Comparative Example 4;

[0110] from Figure 12 and Figure 13It can be seen that with the increase of stirring speed, the coverage rate shows a trend of first increasing and then decreasing, while the operating temperature fluctuates. When the stirring speed is 800r / min, the operating temperature of the microcapsules is 73.6℃, and the coverage rate reaches the best of 85%.

[0111] Comparative Example 5

[0112] The same as Example 1, except that the core material tea polyphenols are replaced by proanthocyanidins (HM-PC), tea polyphenols (HM-GTP), ethylenediaminetetraacetic acid (HM-EDTA), citric acid (HM-CA), vitamin C (HM-VC), melatonin (HM-MT) and β-carotene.

[0113] Figure 14 The graph shows the variation characteristics of the thermal diffusivity of the original coal sample and the retardant coal sample using seven different core materials in comparative example 5. As can be seen from the graph, the thermal diffusivity of the core material with tea polyphenols is the lowest.

[0114] In summary, the present invention investigated the inhibitory effects of different addition levels of antioxidant microcapsules on coal spontaneous combustion, comprehensively analyzing multiple indicators such as oxygen consumption rate, characteristic gas release, inhibition rate, and activation energy, and confirmed that 10% was the optimal addition concentration. Experimental results show that a 10% addition reduced the oxygen consumption rate of coal samples at approximately 90°C, and reduced the CO and CO2 release rates to 43.2% and 50.6% of the original coal, respectively, while achieving an inhibition rate of 87.5%. This excellent inhibitory performance stems from the synergistic effect of the microcapsules at the critical temperature: the capsule wall material PEG-NaHCO3 decomposes and releases heat, isolates oxygen, and dilutes the oxygen concentration. By optimizing the inhibitor addition ratio, the present invention effectively inhibits the entire coal spontaneous combustion process. Experiments have demonstrated that the unique temperature-responsive properties of a 10% addition automatically trigger multiple flame-retardant mechanisms at the critical temperature (approximately 70°C). This invention utilizes environmentally friendly materials, has a simple and efficient preparation process, and can be produced on a large scale without the need for specialized equipment. The raw materials used are widely available, low-cost, and biodegradable, fully meeting the requirements of green mine construction. At the same time, the inhibitor will not produce secondary pollution after exerting its flame retardant effect, and can meet the dual needs of environmental protection and safety in mine fire prevention and firefighting operations.

[0115] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing an antioxidant temperature-activated microcapsule inhibitor for inhibiting coal spontaneous combustion, characterized in that: Tea polyphenols are used as core material, polyethylene glycol and sodium bicarbonate are used as wall materials, and an antioxidant temperature-induced microcapsule inhibitor with a coverage rate of 85% is obtained through microcapsule assembly. Among them, the volume ratio of core material to wall material is 1:3; The volume ratio of polyethylene glycol and sodium bicarbonate is 7:3; The parameters during the microcapsule assembly process were: injection speed of 2 mL / min and stirring speed of 800 r / min.

2. The method for preparing the antioxidant temperature-activated microcapsule inhibitor for inhibiting coal spontaneous combustion according to claim 1, characterized in that: The method specifically comprises the following steps: Adding tea polyphenol powder to deionized water and stirring at a constant temperature to obtain a tea polyphenol solution; Pour the sodium bicarbonate solution into molten polyethylene glycol and stir at constant temperature to obtain PEG-NaHCO3 prepolymer; Using a syringe pump, mixing the prepolymer and the tea polyphenol solution while stirring to obtain a mixed solution; The mixed solution is solidified and dried, ground and sieved to obtain an antioxidant temperature-activated microcapsule inhibitor.

3. The method for preparing the antioxidant temperature-activated microcapsule inhibitor for inhibiting coal spontaneous combustion according to claim 2, characterized in that: The conditions for preparing the tea polyphenol solution are: stirring in a water bath at 60° C. and 800 rpm for 1 hour.

4. The method for preparing the antioxidant temperature-activated microcapsule inhibitor for inhibiting coal spontaneous combustion according to claim 2, characterized in that: The specific preparation steps of the molten polyethylene glycol include: heating the polyethylene glycol in a constant temperature water bath at 70° C. until it is molten.

5. The method for preparing the antioxidant temperature-activated microcapsule inhibitor for inhibiting coal spontaneous combustion according to claim 2, characterized in that: The conditions for preparing the PEG-NaHCO3 prepolymer are as follows: stirring in a water bath at 60°C and 800 rpm for 1 hour.

6. The method for preparing the antioxidant temperature-activated microcapsule inhibitor for inhibiting coal spontaneous combustion according to claim 2, characterized in that: The injection speed of the injection pump during use was 2 mL / min, and the stirring speed was controlled at 800 r / min to form a stable emulsification system.

7. The method for preparing the antioxidant temperature-activated microcapsule inhibitor for inhibiting coal spontaneous combustion according to claim 2, characterized in that: The specific operation steps of the curing and drying are: transferring the mixed solution to a constant temperature water bath at 55°C, maintaining a stirring speed of 800 r / min to continue the reaction for 20-24 hours to complete the curing, and then placing it in a 45°C forced air drying oven to dry for 12 hours; and / or, The grinding and screening refers to passing through a 200-mesh sieve after grinding.

8. An antioxidant temperature-induced microcapsule inhibitor prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the antioxidant temperature-activated microcapsule inhibitor according to claim 8 in the field of preventing and controlling coal spontaneous combustion disasters.

10. The use according to claim 9, characterized in that The added amount of the antioxidant temperature-stimulated microcapsule inhibitor is 4-19% of the mass of the coal sample.

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