Temperature-controlled carbon dioxide release type fire preventing and extinguishing gel as well as preparation method and application thereof

Abstract

The invention discloses a temperature-controlled carbon dioxide release type fire preventing and extinguishing gel and a preparation method and application thereof, and belongs to the technical field of coal mine fire preventing and extinguishing. The hydrogen bond acceptor and the hydrogen bond donor are mixed to obtain the eutectic solvent; mixing water with polyvinyl alcohol to obtain a polyvinyl alcohol aqueous solution; mixing the eutectic solvent with a polyvinyl alcohol aqueous solution, and introducing carbon dioxide until the mass is not increased any more to obtain a gel precursor solution; a cross-linking agent aqueous solution is added into the gel precursor solution to be mixed, after mixing and stirring, standing is carried out, a cross-linking reaction is carried out, temperature-controlled carbon dioxide release type fire preventing and extinguishing gel is formed, the temperature-controlled carbon dioxide release type fire preventing and extinguishing gel wraps a coal body to isolate oxygen, and meanwhile released carbon dioxide cooperatively extinguishes fire. The method is simple in steps, convenient to use and good in fire preventing and extinguishing effect and has a carbon sequestration effect.

Description

Technical Field

[0001] The invention belongs to the technical field of coal mine fire prevention and extinguishing, and particularly relates to a temperature-controlled carbon dioxide-releasing fire prevention and extinguishing gel, and a preparation method and application thereof. Background Art

[0002] In the aerobic environment of goafs, coal undergoes an oxidation reaction with oxygen, storing heat and causing a slow rise in coal temperature. Once the coal temperature exceeds a critical temperature, it experiences a dramatic rise in temperature and spontaneous combustion. CO₂, a major greenhouse gas, has contributed to the global warming effect in recent years. Carbon capture, utilization, and storage (CCUS) technology is an effective means of addressing this greenhouse effect. Furthermore, CO₂, as an inert gas, inhibits coal spontaneous combustion. Chemical absorption, as a key CCUS technology, is currently attracting increasing attention.

[0003] As a chemical absorbent, deep eutectic solvent (DES) is a liquid formed by hydrogen bond donors and hydrogen bond acceptors through hydrogen bonds. It exhibits the characteristics of low volatility, non-corrosiveness, low toxicity, easy preparation and adjustable structure in CO2 capture.

[0004] Prior art publication number CN106280164A discloses a mine-use fire-extinguishing polymer material, a mine-use fire-extinguishing gel material, and their applications. The mine-use fire-extinguishing polymer material comprises, by mass percentage, 25% to 35% sodium polyacrylate particles, 60% to 70% solid powder filler, and 5% flame retardant. The mine-use fire-extinguishing gel material is prepared by mixing the mine-use fire-extinguishing polymer material with water in a mass ratio of 1:100 to 150. The fire-extinguishing material of the present invention is suitable for preventing and controlling coal spontaneous combustion in various situations, integrating leak plugging, cooling, and coal rock strengthening. However, its fire-extinguishing effectiveness is poor, as the gel can only extinguish fires by isolating the coal from oxygen. The fire-extinguishing effectiveness decreases after dehydration, and the gel does not have a carbon fixation effect. Summary of the Invention

[0005] To address the shortcomings of the existing technology, the present invention provides a temperature-controlled carbon dioxide-releasing fire-fighting gel, its preparation method, and its application. This fire-fighting gel absorbs carbon dioxide at room temperature and pressure, and releases CO2 gas when passing through high-temperature areas of a fire zone, synergistically inhibiting the coal. Beyond high-temperature areas of a fire zone, the CO2 remains sealed in the gel. This reduces CO2 emissions while further broadening the application scenarios of deep eutectic solvents. The components used are environmentally friendly, the raw materials are non-toxic and harmless, and are widely available, making them cost-effective.

[0006] To achieve the above objectives, the present invention provides a method for preparing a temperature-controlled carbon dioxide-releasing fire extinguishing gel, which comprises the following steps:

[0007] S1. Mixing a hydrogen bond acceptor and a hydrogen bond donor in a molar ratio of 1:(1-8), heating and stirring at 60° C. to 110° C. for 1-3 hours, and cooling to room temperature to obtain a deep eutectic solvent;

[0008] S2, mixing water and polyvinyl alcohol in a mass ratio of 1: (0.05-0.2), heating and stirring at 80° C. to 95° C. for 2-3 hours until dissolved, and standing and cooling for 12 hours to obtain a polyvinyl alcohol aqueous solution;

[0009] S3, mixing the deep eutectic solvent and the polyvinyl alcohol aqueous solution in a mass ratio of 1:(1-5) and stirring them uniformly, and introducing carbon dioxide until the mass no longer increases, to obtain a gel precursor solution;

[0010] S4. When it is detected that the detection gas concentration at the working face exceeds the threshold value, a cross-linking agent aqueous solution with a mass fraction of 0.5% to 5% is added to the gel precursor solution for mixing, and the mass ratio of the cross-linking agent to the gel precursor solution is 1: (3 to 15); after mixing and stirring, the mixture is allowed to stand for a cross-linking reaction to form a temperature-controlled carbon dioxide-releasing fire-proof gel. The temperature-controlled carbon dioxide-releasing fire-proof gel is wrapped around the surface of the coal body to isolate the air, and releases carbon dioxide after reaching the threshold temperature to cooperate in extinguishing the fire. Even after the gel loses water, it still forms a flame-retardant gel film to wrap the coal body and isolate oxygen.

[0011] Furthermore, the hydrogen bond acceptor includes a mixture of one or more of choline chloride, zinc chloride, lysine, arginine, glycine, glutamic acid, serine, histidine, tryptophan, proline, aspartic acid or betaine.

[0012] Furthermore, the hydrogen bond donor includes a mixture of one or more of urea, polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, ethylene glycol, propylene glycol, glycerol, butanediol, acetic acid, lactic acid, oxalic acid, citric acid or phenol.

[0013] Furthermore, the melting point of the selected deep eutectic solvent needs to be lower than 20°C.

[0014] Furthermore, the cross-linking agent is borax or boric acid.

[0015] Furthermore, the mass ratio of the cross-linker aqueous solution and the gel precursor solution needs to be determined based on whether the carbon-fixing fire-fighting gel containing the low eutectic solvent is formed within the specified time. The higher the proportion of the precursor solution, the slower the reaction rate. When preventing coal spontaneous combustion, the cross-linking reaction is controlled within 5 to 10 minutes. When extinguishing high-temperature fire sources or sealing leaks, the cross-linking is controlled within 0.5 to 3 minutes.

[0016] The invention discloses a method for preparing a temperature-controlled carbon dioxide-releasing fire-proofing gel, and provides a temperature-controlled carbon dioxide-releasing fire-proofing gel.

[0017] An application of the temperature-controlled carbon dioxide fire-fighting gel as described in claim 7, when there is suspected tendency of spontaneous combustion in the goaf, the temperature-controlled carbon dioxide fire-fighting gel is injected upstream of the suspected high-temperature area, when the temperature-controlled carbon dioxide fire-fighting gel flows through and covers the high-temperature area of ​​the coal body, the temperature-controlled carbon dioxide fire-fighting gel releases the stored carbon dioxide gas to assist in fire extinguishing as the temperature of the coal body in the injection area rises, and at the same time, the temperature-controlled carbon dioxide fire-fighting gel wraps the coal body to isolate oxygen, and even if it loses water due to high temperature, it still forms a flame-retardant dense gel film that wraps the surface of the coal body to form a flame-retardant protective layer, continues to isolate the combustible area from oxygen and assists in cooling, and the gel will wrap the coal body to cool it; the temperature range of releasing carbon dioxide gas is 40°C to 130°C, and reaches a peak at 80°C; when the temperature-controlled carbon dioxide fire-fighting gel does not flow through the high-temperature area, the carbon dioxide fixed in the gel will be sealed in the gel all the time, thereby achieving the purpose of sealing carbon dioxide.

[0018] An application of a temperature-controlled carbon dioxide-releasing fire-fighting gel, which is stored in an underground goaf to achieve a carbon fixation effect.

[0019] Beneficial effects:

[0020] 1. The present invention combines a low eutectic solvent with hydrogel technology. Compared with traditional hydrogels, the present invention not only inherits the excellent water retention, fluidity, adhesion to coal and cooling ability, but also gives full play to the characteristics of the low eutectic solvent to destroy hydrogen bonds in coal, dissolve the active ingredients in coal, and thus reduce the low-temperature oxidation intensity of coal. At the same time, the gel can release CO2 at high temperature, and together with the gel, it synergistically inhibits the coal, making it show a more significant effect in inhibiting coal oxidation.

[0021] 2. This invention leverages the properties of a deep eutectic solvent to impart CO2 absorption to the gel. Furthermore, the gel can fix CO2 at low temperatures and release it at high temperatures, enhancing the proactive prevention and control of coal mine fires while providing new insights into reducing carbon emissions. This invention maximizes the synergistic effects of different functional materials, providing a "carbon fixation-gelation-temperature control and resistance" fire prevention and extinguishing material for coal mine fire prevention and extinguishing, meeting mine safety requirements while also aligning with the trend of green, low-carbon development.

[0022] 3. The raw materials used in the present invention are widely available, low-cost, and non-toxic. The deep eutectic solvent used can be prepared by simply mixing and heating in a certain molar ratio, and the carbon dioxide adsorption process is carried out at room temperature and pressure. The preparation process is simple and convenient for large-scale production. It has important promotion value and application prospects in the field of fire extinguishing materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Fourier transform infrared spectra of coal samples wrapped in the temperature-controlled carbon dioxide-releasing fire-fighting gel prepared in Example 1 of the present invention before and after CO2 adsorption and coal samples soaked in water.

[0024] Figure 2 This is a comparison chart of the amount of CO2 adsorbed at different temperatures by the temperature-controlled carbon dioxide-releasing fire extinguishing gel prepared in Example 1 of the present invention.

[0025] Figure 3 TG-DTG curves of the temperature-controlled carbon dioxide-releasing fire extinguishing gel prepared in Example 1 of the present invention before and after CO2 adsorption.

[0026] Figure 4 This is a comparison chart of the programmed temperature-increasing CO2 release of the temperature-controlled carbon dioxide-releasing fire-fighting gel prepared in Example 1 of the present invention before and after CO2 adsorption by the wrapped coal sample and the original coal sample.

[0027] Figure 5 This is a physical picture of the temperature-controlled carbon dioxide-releasing fire extinguishing gel prepared in Example 1 of the present invention after gelation.

[0028] Figure 6 This is a scene photo of the temperature-controlled carbon dioxide-releasing fire-fighting gel prepared in Example 1 of the present invention extinguishing high-temperature burning coal blocks.

[0029] Figure 7 This is a SEM image of a coal block after the temperature-controlled carbon dioxide-releasing fire extinguishing gel prepared in Example 1 of the present invention extinguished a high-temperature burning coal block. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0032] Example 1

[0033] This embodiment provides a temperature-controlled carbon dioxide-releasing fire extinguishing gel and its preparation method and application, which is prepared according to the following steps:

[0034] (1) Choline chloride, lysine, and urea were mixed in a molar ratio of 1:1:2, heated and stirred at 85°C at a speed of 1000 rpm for 2 h, and allowed to stand and cool to room temperature to obtain a deep eutectic solvent;

[0035] (2) mixing water and polyvinyl alcohol in a mass ratio of 1:0.06, heating and stirring at 90°C and 1500 rpm until dissolved, and standing and cooling for 12 hours to obtain a polyvinyl alcohol aqueous solution;

[0036] (3) mixing the deep eutectic solvent prepared in step (1) and step (2) with the polyvinyl alcohol aqueous solution in a mass ratio of 1:4 and stirring them uniformly, and introducing carbon dioxide until the mass no longer increases to obtain a gel precursor solution;

[0037] (4) adding a 2% by mass borax aqueous solution to the saturated carbon dioxide precursor solution prepared in step (3), wherein the mass ratio of the borax aqueous solution to the carbon dioxide precursor solution is 1:10, mixing and stirring, and then standing for a period of time to produce a cross-linking reaction to obtain a temperature-controlled carbon dioxide-releasing fire extinguishing gel.

[0038] When a goaf is suspected of spontaneous combustion, the temperature-controlled carbon dioxide fire-fighting gel is injected upstream of the suspected high-temperature zone. When the gel flows through and covers the high-temperature zone of the coal, it cools the coal and releases carbon dioxide gas for synergistic inhibition. When the gel does not flow through the high-temperature zone, the carbon dioxide trapped within the gel remains sealed within it, achieving its purpose of sealing the carbon dioxide.

[0039] Example 2

[0040] This embodiment provides a temperature-controlled carbon dioxide-releasing fire extinguishing gel. The preparation method thereof is different from that of Example 1 in that, in step (2), the mass ratio of water to polyvinyl alcohol is 1:0.8; in step (3), the mass ratio of the low eutectic solvent to the polyvinyl alcohol aqueous solution is 1:2; and in step (4), the mass fraction of the borax aqueous solution is 0.75%, and the mass ratio of the borax aqueous solution to the gel precursor solution is 1:5.

[0041] Example 3

[0042] This embodiment provides a temperature-controlled carbon dioxide-releasing fire extinguishing gel. The preparation method thereof is different from that of Example 1 in that, in step (1), the molar ratio of choline chloride, lysine, and urea is 1:0.5:2; in step (2), the mass ratio of water to polyvinyl alcohol is 1:0.08; in step (3), the mass ratio of the low eutectic solvent to the polyvinyl alcohol aqueous solution is 1:3; and in step S5, the mass fraction of the borax aqueous solution is 0.8%, and the mass ratio of the borax aqueous solution to the carbon dioxide precursor solution is 1:4.

[0043] Example 4

[0044] This embodiment provides a temperature-controlled carbon dioxide-releasing fire extinguishing gel. The preparation method thereof is different from that of Example 1 in that, in step (1), the molar ratio of choline chloride, lysine, and urea is 1:0.75:2; in step (3), the mass ratio of the low eutectic solvent to the polyvinyl alcohol aqueous solution is 1:2; and in step (4), the mass fraction of the borax aqueous solution is 3%, and the mass ratio of the borax aqueous solution to the carbon dioxide precursor solution is 1:15.

[0045] Example 5

[0046] This embodiment provides a temperature-controlled carbon dioxide-releasing fire extinguishing gel and its preparation method and application, which is prepared according to the following steps:

[0047] (1) Choline chloride, glutamic acid, and polyethylene glycol 200 were mixed in a molar ratio of 1:0.3:2, heated and stirred at 80°C at a speed of 1000 rpm for 2 h, and allowed to stand and cool to room temperature to obtain a deep eutectic solvent;

[0048] (2) mixing water and polyvinyl alcohol in a mass ratio of 1:0.07, heating and stirring at 90°C and 1500 rpm until dissolved, and standing and cooling for 12 hours to obtain a polyvinyl alcohol aqueous solution;

[0049] (3) mixing the deep eutectic solvent prepared in step (1) and step (2) with the polyvinyl alcohol aqueous solution in a mass ratio of 1:4 and stirring them uniformly, and introducing carbon dioxide until the mass no longer increases to obtain a gel precursor solution;

[0050] (4) adding a 3% by mass borax aqueous solution to the saturated carbon dioxide precursor solution prepared in step (3), wherein the mass ratio of the borax aqueous solution to the carbon dioxide precursor solution is 1:8, mixing and stirring, and then standing for a period of time to produce a cross-linking reaction to obtain a temperature-controlled carbon dioxide-releasing fire extinguishing gel.

[0051] When a goaf is suspected of spontaneous combustion, the temperature-controlled carbon dioxide fire-fighting gel is injected upstream of the suspected high-temperature zone. When the gel flows through and covers the high-temperature zone of the coal, it cools the coal and releases carbon dioxide gas for synergistic inhibition. When the gel does not flow through the high-temperature zone, the carbon dioxide trapped within the gel remains sealed within it, achieving its purpose of sealing the carbon dioxide.

[0052] Example 6

[0053] This embodiment provides a temperature-controlled carbon dioxide-releasing fire extinguishing gel and its preparation method and application, which is prepared according to the following steps:

[0054] (1) Choline chloride, proline, and polyethylene glycol 400 were mixed in a molar ratio of 1:0.5:5, heated and stirred at 85°C at a speed of 1200 rpm for 2 h, and allowed to stand and cool to room temperature to obtain a deep eutectic solvent;

[0055] (2) mixing water and polyvinyl alcohol in a mass ratio of 1:0.07, heating and stirring at 87°C and 1500 rpm until dissolved, and standing and cooling for 12 hours to obtain a polyvinyl alcohol aqueous solution;

[0056] (3) mixing the deep eutectic solvent prepared in step (1) and step (2) with the polyvinyl alcohol aqueous solution in a mass ratio of 1:3 and stirring them uniformly, and introducing carbon dioxide until the mass no longer increases to obtain a gel precursor solution;

[0057] (4) adding a 2% by mass borax aqueous solution to the saturated carbon dioxide precursor solution prepared in step (3), wherein the mass ratio of the borax aqueous solution to the carbon dioxide precursor solution is 1:7, mixing and stirring, and then standing for a period of time to produce a cross-linking reaction to obtain a temperature-controlled carbon dioxide-releasing fire extinguishing gel.

[0058] When a goaf is suspected of spontaneous combustion, the temperature-controlled carbon dioxide fire-fighting gel is injected upstream of the suspected high-temperature zone. When the gel flows through and covers the high-temperature zone of the coal, it cools the coal and releases carbon dioxide gas for synergistic inhibition. When the gel does not flow through the high-temperature zone, the carbon dioxide trapped within the gel remains sealed within it, achieving its purpose of sealing the carbon dioxide.

[0059] Example 7

[0060] This embodiment provides a temperature-controlled carbon dioxide-releasing fire extinguishing gel and its preparation method and application, which is prepared according to the following steps:

[0061] (1) betaine, aspartic acid, and lactic acid were mixed in a molar ratio of 1:0.2:5, heated and stirred at 90°C and 1500 rpm for 2 h, and allowed to stand and cool to room temperature to obtain a deep eutectic solvent;

[0062] (2) mixing water and polyvinyl alcohol in a mass ratio of 1:0.08, heating and stirring at 90°C and 1500 rpm until dissolved, and standing and cooling for 12 hours to obtain a polyvinyl alcohol aqueous solution;

[0063] (3) mixing the deep eutectic solvent prepared in step (1) and step (2) with the polyvinyl alcohol aqueous solution in a mass ratio of 1:5 and stirring them uniformly, and introducing carbon dioxide until the mass no longer increases to obtain a gel precursor solution;

[0064] (4) adding a 4% by mass borax aqueous solution to the saturated carbon dioxide precursor solution prepared in step (3), wherein the mass ratio of the borax aqueous solution to the carbon dioxide precursor solution is 1:15, mixing and stirring, and then standing for a period of time to produce a cross-linking reaction to obtain a temperature-controlled carbon dioxide-releasing fire extinguishing gel.

[0065] When a goaf is suspected of spontaneous combustion, the temperature-controlled carbon dioxide fire-fighting gel is injected upstream of the suspected high-temperature zone. When the gel flows through and covers the high-temperature zone of the coal, it cools the coal and releases carbon dioxide gas for synergistic inhibition. When the gel does not flow through the high-temperature zone, the carbon dioxide trapped within the gel remains sealed within it, achieving its purpose of sealing the carbon dioxide.

[0066] Example 8

[0067] This embodiment provides a temperature-controlled carbon dioxide-releasing fire extinguishing gel and its preparation method and application, which is prepared according to the following steps:

[0068] (1) Proline and citric acid were mixed in a molar ratio of 1:2, heated and stirred at 85°C at a speed of 1200 rpm for 2 h, and allowed to stand and cool to room temperature to obtain a deep eutectic solvent;

[0069] (2) mixing water and polyvinyl alcohol in a mass ratio of 1:0.07, heating and stirring at 90°C and 1300 rpm until dissolved, and standing and cooling for 12 hours to obtain a polyvinyl alcohol aqueous solution;

[0070] (3) mixing the deep eutectic solvent prepared in step (1) and step (2) with the polyvinyl alcohol aqueous solution in a mass ratio of 1:4 and stirring them uniformly, and introducing carbon dioxide until the mass no longer increases to obtain a gel precursor solution;

[0071] (4) adding a 0.8% by mass borax aqueous solution to the saturated carbon dioxide precursor solution prepared in step (3), wherein the mass ratio of the borax aqueous solution to the carbon dioxide precursor solution is 1:6, mixing and stirring, and then standing for a period of time to produce a cross-linking reaction to obtain a temperature-controlled carbon dioxide-releasing fire extinguishing gel.

[0072] When a goaf is suspected of spontaneous combustion, the temperature-controlled carbon dioxide fire-fighting gel is injected upstream of the suspected high-temperature zone. When the gel flows through and covers the high-temperature zone of the coal, it cools the coal and releases carbon dioxide gas for synergistic inhibition. When the gel does not flow through the high-temperature zone, the carbon dioxide trapped within the gel remains sealed within it, achieving its purpose of sealing the carbon dioxide.

[0073] Example 9

[0074] This embodiment provides a temperature-controlled carbon dioxide-releasing fire extinguishing gel and its preparation method and application, which is prepared according to the following steps:

[0075] (1) zinc chloride, histidine, and acetic acid were mixed in a molar ratio of 1:0.3:2, heated and stirred at 85°C at a speed of 1200 rpm for 2 h, and allowed to stand and cool to room temperature to obtain a deep eutectic solvent;

[0076] (2) mixing water and polyvinyl alcohol in a mass ratio of 1:0.09, heating and stirring at 80°C and 1500 rpm until dissolved, and standing and cooling for 12 hours to obtain a polyvinyl alcohol aqueous solution;

[0077] (3) mixing the deep eutectic solvent prepared in step (1) and step (2) with the polyvinyl alcohol aqueous solution in a mass ratio of 1:2 and stirring them uniformly, and introducing carbon dioxide until the mass no longer increases to obtain a gel precursor solution;

[0078] (4) adding a 2.5% by mass borax aqueous solution to the saturated carbon dioxide precursor solution prepared in step (3), wherein the mass ratio of the borax aqueous solution to the carbon dioxide precursor solution is 1:12, mixing and stirring, and then standing for a period of time to produce a cross-linking reaction to obtain a temperature-controlled carbon dioxide-releasing fire extinguishing gel.

[0079] When a goaf is suspected of spontaneous combustion, the temperature-controlled carbon dioxide fire-fighting gel is injected upstream of the suspected high-temperature zone. When the gel flows through and covers the high-temperature zone of the coal, it cools the coal and releases carbon dioxide gas for synergistic inhibition. When the gel does not flow through the high-temperature zone, the carbon dioxide trapped within the gel remains sealed within it, achieving its purpose of sealing the carbon dioxide.

[0080] like Figure 1 As shown in the figure, the Fourier transform infrared spectra of the coal sample wrapped and soaked in water before and after the temperature-controlled carbon dioxide release fire extinguishing gel prepared in Example 1 adsorbs CO2 are shown, with the wave number range of 3340 cm -1 This corresponds to the hydrogen bond between molecules, where the strength is: gel after carbon dioxide adsorption + coal < gel before carbon dioxide adsorption + coal < water + coal, indicating that gel adsorption of carbon dioxide can reduce the strength of hydrogen bonds in coal; Figure 1 The red line represents the Fourier transform infrared spectrum of the gel-soaked coal sample prepared by directly proceeding to step S4 without adsorbing CO2 through step S3. The blue line represents the Fourier transform infrared spectrum of the gel-soaked coal sample prepared after adsorbing CO2 through the normal preparation process. The black line represents the Fourier transform infrared spectrum of the water-soaked coal sample.

[0081] like Figure 2As shown, a comparison chart of the amount of CO2 adsorbed by the temperature-controlled carbon dioxide-releasing fire extinguishing gel prepared in Example 1 at different temperatures is shown, indicating that the gel has the largest CO2 adsorption amount at 40°C, and the adsorption amount will decrease at higher temperatures, and the CO2 in the gel will be released, and the amount of carbon dioxide released will also increase with increasing temperature. Figure 4 The data show that the amount of carbon dioxide released can account for 5% of the air content under ventilation conditions. If there is no ventilation, carbon dioxide will accumulate on the coal body because it is heavier than air, and the content will be higher. Figure 5 This is the actual object of the temperature-controlled carbon dioxide-releasing fire-fighting gel after it is gelled. As can be seen from the attached figure, the temperature-controlled carbon dioxide-releasing fire-fighting gel has a good adhesion effect and can be well attached to the coal body.

[0082] like Figure 3 As shown, the TG-DTG curves of the temperature-controlled carbon dioxide-releasing fire extinguishing gel prepared in Example 1 before and after CO2 adsorption are shown, indicating that the thermal stability of the gel decreases after carbon dioxide adsorption and carbon dioxide will be released at high temperatures.

[0083] like Figure 4 As shown, a comparison chart of the programmed temperature-increasing CO2 release of the temperature-controlled carbon dioxide-releasing fire-fighting gel prepared in Example 1 before and after CO2 adsorption is shown, indicating that the gel after carbon dioxide adsorption will release CO2 from 40°C to 130°C to participate in inhibiting coal spontaneous combustion; above 150°C is the carbon dioxide released by coal oxidation, and the release amount is: gel after carbon dioxide adsorption + coal < gel before carbon dioxide adsorption + coal < original coal, indicating that the gel after carbon dioxide adsorption has the best inhibitory effect on coal, and can synergistically inhibit the CO2 released at 40°C to 130°C.

[0084] like Figure 6 As shown, a scene picture of the temperature-controlled carbon dioxide-releasing fire-fighting gel prepared in Example 1 extinguishing a high-temperature burning coal block is shown, indicating that after the gel comes into contact with the high-temperature coal block, part of the water evaporates and takes away the heat, while a gel film is formed on the surface of the coal body, effectively isolating oxygen, thereby achieving a fire extinguishing effect.

[0085] like Figure 7 As shown, the SEM image of the coal block after the temperature-controlled carbon dioxide-releasing fire-fighting gel prepared in Example 1 extinguished the high-temperature burning coal block is shown, indicating that after the fire is extinguished, the gel loses water to form a dense gel film that wraps the coal sample, achieving the effect of isolating oxygen.

Claims

1. A method for preparing a temperature-controlled carbon dioxide-releasing fire extinguishing gel, characterized in that: The steps include: S1. Mixing a hydrogen bond acceptor and a hydrogen bond donor in a molar ratio of 1:(1-8), heating and stirring at 60° C. to 110° C. for 1-3 hours, and cooling to room temperature to obtain a deep eutectic solvent; S2, mixing water and polyvinyl alcohol in a mass ratio of 1: (0.05-0.2), heating and stirring at 80° C. to 95° C. for 2-3 hours until dissolved, and standing and cooling for 12 hours to obtain a polyvinyl alcohol aqueous solution; S3, mixing the deep eutectic solvent and the polyvinyl alcohol aqueous solution in a mass ratio of 1:(1-5) and stirring them uniformly, and introducing carbon dioxide until the mass no longer increases, to obtain a gel precursor solution; S4. When it is detected that the detection gas concentration at the working face exceeds the threshold value, a cross-linking agent aqueous solution with a mass fraction of 0.5% to 5% is added to the gel precursor solution for mixing, and the mass ratio of the cross-linking agent to the gel precursor solution is 1: (3 to 15); after mixing and stirring, the mixture is allowed to stand for a cross-linking reaction to form a temperature-controlled carbon dioxide-releasing fire-proof gel. The temperature-controlled carbon dioxide-releasing fire-proof gel is wrapped around the surface of the coal body to isolate the air, and releases carbon dioxide after reaching the threshold temperature to cooperate in extinguishing the fire. Even after the gel loses water, it still forms a flame-retardant gel film to wrap the coal body and isolate oxygen.

2. The method for preparing the temperature-controlled carbon dioxide-releasing fire extinguishing gel according to claim 1, characterized in that: The hydrogen bond acceptor comprises a mixture of one or more of choline chloride, zinc chloride, lysine, arginine, glycine, glutamic acid, serine, histidine, tryptophan, proline, aspartic acid or betaine.

3. The method for preparing the temperature-controlled carbon dioxide-releasing fire extinguishing gel according to claim 1, characterized in that: The hydrogen bond donor includes one or more of urea, polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, ethylene glycol, propylene glycol, glycerol, butanediol, acetic acid, lactic acid, oxalic acid, citric acid or phenol.

4. The method for preparing the temperature-controlled carbon dioxide-releasing fire extinguishing gel according to claim 1, characterized in that: The melting point of the selected deep eutectic solvent should be below 20°C.

5. The method for preparing the temperature-controlled carbon dioxide-releasing fire extinguishing gel according to claim 1, characterized in that: The crosslinking agent is borax or boric acid.

6. The method for preparing the temperature-controlled carbon dioxide-releasing fire extinguishing gel according to claim 1, characterized in that: The mass ratio of the cross-linker aqueous solution and the gel precursor solution needs to be determined based on whether the carbon-fixing fire-fighting gel containing the low eutectic solvent is formed within the specified time. The higher the proportion of the precursor solution, the slower the reaction speed. When preventing coal spontaneous combustion, the cross-linking reaction is controlled within 5 to 10 minutes. When extinguishing high-temperature fire sources or sealing leaks, the cross-linking is controlled within 0.5 to 3 minutes.

7. A temperature-controlled carbon dioxide-releasing fire-extinguishing gel prepared by the method for preparing the temperature-controlled carbon dioxide-releasing fire-extinguishing gel according to claim 1.

8. An application of the temperature-controlled carbon dioxide-releasing fire extinguishing gel according to claim 7, characterized in that: When there is suspected tendency for spontaneous combustion in the goaf, a temperature-controlled carbon dioxide fire-extinguishing gel is injected upstream of the suspected high-temperature area. When the temperature-controlled carbon dioxide fire-extinguishing gel flows through and covers the high-temperature area of ​​the coal body, as the temperature of the coal body in the injection area rises, the temperature-controlled carbon dioxide fire-extinguishing gel will release the stored carbon dioxide gas to assist in fire extinguishing. At the same time, the temperature-controlled carbon dioxide fire-extinguishing gel wraps the coal body to isolate oxygen. Even if it loses water due to high temperature, it still forms a flame-retardant dense gel film that wraps the surface of the coal body to form a flame-retardant protective layer, continuing to isolate the combustible area from oxygen and assisting in cooling. The gel will wrap the coal body to cool it down. The temperature range for releasing carbon dioxide gas is 40℃~130℃, and reaches a peak at 80℃. When the temperature-controlled carbon dioxide fire-extinguishing gel does not flow through the high-temperature area, the carbon dioxide fixed in the gel will be sealed in the gel to achieve the purpose of sealing carbon dioxide.

9. An application of the temperature-controlled carbon dioxide-releasing fire extinguishing gel according to claim 7, characterized in that: The temperature-controlled release of carbon dioxide fire-fighting gel is stored in the underground goaf to achieve the effect of carbon fixation.

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