Inorganic temperature-sensitive dynamic phase-change fire-proof gel material and preparation method thereof

Abstract

The present invention discloses an inorganic temperature-sensitive dynamic phase-change fire-fighting gel material and a preparation method thereof, which belongs to the field of mine fire prevention and extinguishing. Sodium alginate and an acidic agent are dissolved in water and stirred until completely dissolved; a water-soluble organic liquid is mixed with an aqueous solution of sodium alginate and an acidic agent and stirred evenly; calcium chloride is mixed with water to obtain a calcium chloride aqueous solution; a mixed solution of sodium alginate, an acidic agent and a water-soluble organic liquid is dripped into the calcium chloride aqueous solution at a certain speed to form calcium alginate microspheres; sodium silicate is mixed with water and stirred until completely dissolved to obtain a sodium silicate aqueous solution; calcium alginate microspheres are added to the sodium silicate solution to obtain an inorganic temperature-sensitive phase-change suspension. The prepared inorganic temperature-sensitive phase-change suspension is a mixed solution composed of calcium alginate microspheres and sodium silicate solution under low temperature conditions, has strong fluidity, covers all the coal residues to form a slurry layer, and achieves long-term inhibition of low-temperature oxidation of coal and high-temperature flame retardant effect.

Description

Technical Field

[0001] The present invention relates to the field of coal mine technology, specifically an inorganic temperature-sensitive dynamic phase-change fire-proofing gel material and a preparation method thereof. Background Art

[0002] Over 90% of mine fires during coal mining are caused by spontaneous combustion of coal. With the widespread adoption of high-height, fully mechanized mining methods, large cavities are forming in mine goafs. The resulting cavitation and cracks in the delamination provide numerous air leaks into the goaf's coal, making goafs the most vulnerable areas for spontaneous combustion in coal mines. 60% of spontaneous combustion fires occur in goafs. Spontaneous combustion of coal in mines and coalfield fires does not develop uniformly; instead, hot spots are present. These hot spots can form and develop anywhere within the fire zone, gradually shifting with coal mining and crack leakage. If these hot spots are not effectively controlled, they will eventually lead to spontaneous combustion. The complex underground environment creates favorable conditions for spontaneous combustion, making the detection of hot spots more challenging. Therefore, there is an urgent need to develop a material that can automatically identify hot spots within a fire zone and utilize the temperature to sequentially release and target them.

[0003] The State Administration of Coal Mine Safety has issued the "Safety Management Measures for Reactive Polymer Materials in Underground Coal Mines (Trial)", which clearly stipulates that "polymer materials generated by reactions of highly corrosive and highly volatile components shall not be used in underground coal mines, polymer materials with violent chemical reactions and high heat release are prohibited from being used in places where they are in direct contact with coal, and polyurethane foam materials are prohibited from being used in closed filling operations." It can be seen that it is very necessary to find a method to prevent and control coal spontaneous combustion that is environmentally friendly, effective, and economically reasonable. Summary of the Invention

[0004] In order to address the deficiencies of the prior art, the present invention provides an inorganic temperature-sensitive dynamic phase-change fire-fighting gel material and a preparation method thereof. The gel material is initially a liquid with good fluidity. When passing through the high-temperature point in the fire zone, it will form a gel with increased viscosity, thereby achieving targeted retention in the fire zone. The components used will not pollute the environment, are widely available, and have controllable costs.

[0005] To solve the above technical problems, the present invention provides a method for preparing an inorganic temperature-sensitive dynamic phase-change fire-proofing gel material. The fire-extinguishing gel material comprises a large number of calcium alginate microspheres suspended in a sodium silicate aqueous solution. At room temperature, the sodium alginate solution encapsulated in the calcium alginate microspheres in the suspension is separated from the sodium silicate solution substrate and does not contact it. When exposed to high temperatures, the two automatically mix to extinguish the fire.

[0006] The following steps are involved:

[0007] 1) Pour sodium alginate and acidic reagent into water and stir until completely dissolved to obtain a seaweed mixed solution, wherein the mass ratio of sodium alginate, acidic reagent and water is (0.02-0.04): (0.2-0.4): 1

[0008] 2) Fully mix the water-soluble organic liquid with a boiling point of 45-80°C with the seaweed mixed solution. The mass ratio of the water-soluble organic liquid to the sodium alginate solution is 0.2-0.5:1.

[0009] 3) mixing calcium chloride with water to obtain a calcium chloride aqueous solution, wherein the mass ratio of calcium chloride to water is (0.02-0.04):1;

[0010] 4) dropping the seaweed mixed solution mixed with the water-soluble organic liquid in step 2) into a calcium chloride aqueous solution, whereby the sodium alginate at the interface between the liquid seaweed mixed solution and the calcium chloride aqueous solution reacts rapidly with the calcium chloride to solidify into calcium alginate. The generated outer layer of calcium alginate prevents further reaction, ultimately forming calcium alginate microspheres in the calcium chloride aqueous solution. The outer layer of the calcium alginate microspheres is the generated calcium alginate, and the inner layer is a mixed solution of the water-soluble organic liquid and the sodium alginate solution.

[0011] 5) After the calcium alginate microspheres are prepared, they are immediately taken out from the mixed solution and placed in the air to prevent the calcium alginate shell from becoming too thick;

[0012] 6) mixing sodium silicate and water in a mass ratio of 0.03:1 and stirring until completely dissolved to obtain a sodium silicate aqueous solution;

[0013] 7) After calcium alginate microspheres are uniformly mixed into the sodium silicate aqueous solution, an inorganic temperature-sensitive dynamic phase-change fire-proof gel material is obtained, wherein the mass ratio of calcium alginate microspheres to sodium silicate solution is 1:(5-20).

[0014] Furthermore, the acidic reagents include ammonium sulfate, ammonium chloride, hydrochloric acid, oxalic acid, phosphoric acid, hydrofluoric acid, lactic acid, benzoic acid, acetic acid, formic acid, and citric acid. The ratio of the acidic reagents is determined according to the pH value of the acidic substances dissolved in water, ensuring that the pH value of the solution after the acidic reagents react with sodium silicate to form a gel is 6 to 9. The stronger the acidic reagent, the less amount is added. The specific value needs to be determined according to the ratio of calcium alginate microspheres to sodium silicate solution and the hydrogen ion concentration of various acidic substances dissolved in water.

[0015] Furthermore, the boiling point of the water-soluble organic liquid is determined based on the self-heating critical temperature of the coal from the slow oxidation stage to the rapid heating stage, which is less than 60°C for lignite, less than 70°C for bituminous coal, and less than 80°C for anthracite; the water-soluble organic liquid is wrapped in the calcium alginate microspheres and will break through the calcium alginate microspheres when the boiling point of the water-soluble organic liquid is reached.

[0016] Furthermore, the water-soluble organic liquid includes perfluorohexanone, trifluoroacetic acid, tetrahydrofuran, ethylene glycol dimethyl ether, acetonitrile, and isopropyl alcohol, and more preferably perfluorohexanone and trifluoroacetic acid.

[0017] Furthermore, the mass concentration of the calcium chloride solution is 2%-4%.

[0018] Furthermore, the mixed solution of sodium alginate, acidic reagent and water-soluble organic liquid is added at a rate of 40-90 drops / min.

[0019] Furthermore, the diameter of the generated calcium alginate microspheres is 500 μm to 1500 μm. Since the sodium silicate solution is viscous, the calcium alginate microspheres can be protected from breaking during the grouting process.

[0020] The invention discloses an inorganic temperature-sensitive dynamic phase-change fire-proofing and extinguishing gel material prepared by a preparation method thereof.

[0021] An application of an inorganic temperature-sensitive dynamic phase-change fire-proofing and extinguishing gel material, which is sprayed into the goaf and flows through all the residual coal, so that the inorganic temperature-sensitive dynamic phase-change fire-proofing and extinguishing gel material flows through all the residual coal and covers it. When the residual coal area in the goaf is smoldering and a high-temperature area appears, that is, when the coal temperature reaches the critical temperature for turning to the rapid oxidation stage, the water-soluble organic liquid wrapped in the calcium alginate microspheres reaches the boiling point and vaporizes to break through the calcium alginate microspheres, releasing an acidic reagent aqueous solution to react with the sodium silicate solution to form a viscous silica colloid. The formed inorganic temperature-sensitive phase-change gel adheres to the high-temperature area, realizes the targeted identification and retention of high-temperature points in the fire area, and realizes long-term inhibition of low-temperature oxidation of coal and high-temperature flame retardant effect.

[0022] An application of an inorganic temperature-sensitive dynamic phase-change fire-proofing gel material, spraying the inorganic temperature-sensitive dynamic phase-change fire-proofing gel material upstream of a suspected high-temperature area in a goaf, so that when the inorganic temperature-sensitive dynamic phase-change fire-proofing gel material flows through the suspected high-temperature area, if the temperature of the suspected high-temperature area reaches the phase change temperature of the inorganic temperature-sensitive dynamic phase-change fire-proofing gel material, the solid microcapsules in the inorganic temperature-sensitive dynamic phase-change fire-proofing gel material will melt, releasing acidic salts to react with sodium silicate in the suspension to form a viscous silica colloid, the fluidity of which is weakened, and the inorganic temperature-sensitive dynamic phase-change fire-proofing gel material accumulates at high temperatures, thereby completing the rapid identification and retention of the truly high-temperature area.

[0023] Beneficial effects

[0024] Compared with the prior art, the inorganic temperature-sensitive dynamic phase-change fire-proofing gel material and its preparation method provided by the present invention have the following advantages:

[0025] The gel formed by the inorganic temperature-sensitive phase change material of the present invention is odorless, does not pollute the environment, has a wide range of sources, is inexpensive and controllable, and has a simple and efficient production process. Sodium alginate is a natural high-molecular polysaccharide made from brown algae plants through a series of processing and extraction. It has thickening properties, thermal stability, and gel properties. Due to the excellent performance and wide sources of sodium alginate, it is widely used in the food industry, sewage treatment, medical field and other industries. Sodium alginate solution can undergo ion exchange reaction with divalent calcium ions to form calcium alginate microspheres. Gel sodium silicate is a water-soluble silicate that can be used as an adhesive for cardboard, wood, and refractory materials. It is used in glass manufacturing to make glass more fire-resistant and corrosion-resistant. It can also be used to manufacture biodegradable environmentally friendly materials and can react with acidic substances to form silica gel. The present invention releases calcium alginate microspheres through temperature control, so that the sodium silicate aqueous solution forms silica gel, which can realize that the initial state of the gel material is a liquid with good fluidity. When passing through the high temperature point in the fire zone, a gel will be formed, and the viscosity increases, thereby achieving targeted retention in the fire zone. Compared with organic thermosensitive phase change gels, the inorganic sodium silicate gel provided by the present invention has a fast gelling speed, good initial fluidity, low price, safety and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the principle of the release of a mixed solution by high-temperature rupture of calcium alginate microspheres in the inorganic temperature-sensitive dynamic phase-change fire extinguishing gel of the present invention;

[0027] Figure 2 This is a photo of the calcium alginate microspheres in the inorganic temperature-sensitive dynamic phase-change fire extinguishing gel in an embodiment of the present invention rupturing at high temperature to release a mixed solution;

[0028] Figure 3 Schematic diagram of the rupture of calcium alginate microspheres in the inorganic temperature-sensitive dynamic phase-change fire extinguishing gel in an embodiment of the present invention to release an acidic solution that reacts with sodium silicate to form a gel.

[0029] Figure: 1. Calcium alginate shell, 2. Mixed solution of sodium alginate, acidic reagent, and water-soluble organic liquid Specific implementation plan

[0030] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0031] The present invention discloses a method for preparing an inorganic temperature-sensitive dynamic phase-change fire-proofing gel material. The prepared inorganic temperature-sensitive dynamic phase-change fire-proofing gel material is as follows: Figure 2 and Figure 3 As shown,

[0032] Example 1

[0033] For lignite, its self-heating critical temperature is about 60°C, so it is necessary to prepare a phase change gel with a phase change temperature below 60°C to prevent the rapid oxidation of lignite.

[0034] An inorganic temperature-sensitive dynamic phase-change fire-fighting gel material is prepared by mixing sodium alginate, ammonium chloride, and water in a mass ratio of 0.03:0.6:1 and stirring thoroughly to completely dissolve the sodium alginate and ammonium chloride. Perfluorohexanone is mixed with an aqueous solution of sodium alginate and ammonium chloride in a mass ratio of 0.2:1 and stirred thoroughly. Calcium chloride is mixed with water in a mass ratio of 0.02:1 and stirred thoroughly. An aqueous solution of perfluorohexanone, sodium alginate, and ammonium chloride is dripped into a calcium chloride solution at a rate of 50 drops / min to obtain calcium alginate microspheres, and the microspheres are immediately removed from the aqueous solution. Sodium silicate with a modulus of 2 is stirred thoroughly with water in a mass ratio of 0.03:1 to completely dissolve the sodium silicate. The calcium alginate microspheres are mixed with the sodium silicate solution to obtain an inorganic temperature-sensitive phase-change suspension.

[0035] The above-mentioned inorganic thermosensitive phase change suspension is injected into the goaf through the grouting pipeline. When the suspension reaches the high-temperature point of coal spontaneous combustion and the temperature reaches above 50°C, the perfluorohexanone liquid in the calcium alginate microspheres vaporizes, breaks through the calcium alginate microspheres, and releases ammonium chloride solution to react with sodium silicate to form an inorganic thermosensitive phase change gel. The viscosity of the generated silica gel increases, and it can stay at the high-temperature point in the goaf for a long time.

[0036] Example 2

[0037] For anthracite, its self-heating critical temperature is about 80°C, so it is necessary to prepare a phase change gel with a phase change temperature below 80°C to prevent the rapid oxidation of lignite.

[0038] An inorganic temperature-sensitive dynamic phase-change fire-fighting gel material is prepared by thoroughly stirring sodium alginate, formic acid, and water in a mass ratio of 0.03:0.3:1 to completely dissolve the sodium alginate and formic acid. Trifluoroacetic acid is mixed with an aqueous solution of sodium alginate and formic acid in a mass ratio of 0.3:1 and stirred evenly. Calcium chloride is mixed with water in a mass ratio of 0.02:1 and stirred evenly. The aqueous solution of trifluoroacetic acid, sodium alginate, and formic acid is dripped into a calcium chloride solution at a rate of 60 drops per minute to obtain calcium alginate microspheres, which are then immediately removed from the aqueous solution. Sodium silicate with a modulus of 2.2 is thoroughly stirred with water in a mass ratio of 0.03:1 to completely dissolve the sodium silicate. The calcium alginate microspheres are mixed with the sodium silicate solution to obtain an inorganic temperature-sensitive phase-change suspension.

[0039] The above-mentioned inorganic thermosensitive phase change suspension is injected into the goaf through the grouting pipeline. When the suspension reaches the high-temperature point of coal spontaneous combustion and the temperature reaches above 73°C, the trifluoroacetic acid liquid in the calcium alginate microspheres vaporizes, breaks through the calcium alginate microspheres, and releases ammonium chloride solution to react with sodium silicate to form an inorganic thermosensitive phase change gel. The viscosity of the generated silica gel increases and it can stay in the high-temperature point of the goaf for a long time.

[0040] An application of an inorganic temperature-sensitive dynamic phase-change fire-proofing gel material, which is sprayed into the goaf and flows through all the coal residues, so that the inorganic temperature-sensitive dynamic phase-change fire-proofing gel material flows through all the coal residues and covers them. When the coal residue area in the goaf smolders and a high-temperature area appears, that is, when the coal temperature reaches the critical temperature for turning to the rapid oxidation stage, the water-soluble organic liquid wrapped in the calcium alginate microspheres reaches the boiling point and gasifies to break through the calcium alginate microspheres. Specifically, Figure 1 and Figure 2 As shown in the figure, serial number 1 represents the calcium alginate shell, serial number 2 represents the mixed solution composed of sodium alginate, acidic reagent and water-soluble organic liquid, the released acidic reagent aqueous solution reacts with the sodium silicate solution to form a viscous silicate colloid, and the formed inorganic temperature-sensitive phase change gel adheres to the high-temperature area, realizing the targeted identification and retention of the high-temperature point in the fire zone, as shown in the figure. Figure 3 As shown, long-term inhibition of low-temperature oxidation of coal and high-temperature flame retardant effect are achieved.

[0041] An application of an inorganic temperature-sensitive dynamic phase-change fire-proofing and extinguishing gel material, which is sprayed into the goaf and flows through all the residual coal, so that the inorganic temperature-sensitive dynamic phase-change fire-proofing and extinguishing gel material flows through all the residual coal and covers it. When the residual coal area in the goaf is smoldering and a high-temperature area appears, that is, when the coal temperature reaches the critical temperature for turning to the rapid oxidation stage, the water-soluble organic liquid wrapped in the calcium alginate microspheres reaches the boiling point and vaporizes to break through the calcium alginate microspheres, releasing an acidic reagent aqueous solution to react with the sodium silicate solution to form a viscous silica colloid. The formed inorganic temperature-sensitive phase-change gel adheres to the high-temperature area, realizes the targeted identification and retention of high-temperature points in the fire area, and realizes long-term inhibition of low-temperature oxidation of coal and high-temperature flame retardant effect.

[0042] Spray the inorganic temperature-sensitive dynamic phase-change fire-proof gel material upstream of the suspected high-temperature area in the goaf, so that when the inorganic temperature-sensitive dynamic phase-change fire-proof gel material flows through the suspected high-temperature area, if the temperature of the suspected high-temperature area reaches the phase change temperature of the inorganic temperature-sensitive dynamic phase-change fire-proof gel material, the solid microcapsules in the inorganic temperature-sensitive dynamic phase-change fire-proof gel material will melt, releasing acidic salts to react with sodium silicate in the suspension to form a viscous silica colloid, the fluidity of which is weakened, and it accumulates at high temperatures, thereby completing the rapid identification and retention of the truly high-temperature area.

Claims

1. A method for preparing an inorganic temperature-sensitive dynamic phase-change fire-proofing gel material, characterized by: The fire extinguishing gel material is a large number of calcium alginate microspheres suspended in a sodium silicate aqueous solution. At room temperature, the sodium alginate solution sealed in the calcium alginate microspheres in the suspension is separated from the sodium silicate solution. When exposed to high temperatures, the two automatically mix to extinguish the fire. The following steps are involved: 1) Pour sodium alginate and an acidic reagent into water and stir until completely dissolved to obtain a seaweed mixed solution, wherein the mass ratio of sodium alginate, acidic reagent and water is (0.02-0.04): (0.2-0.4): 1; 2) Thoroughly mix a water-soluble organic liquid with a boiling point of 45-80°C and the seaweed mixed solution, with the mass ratio of the water-soluble organic liquid to the sodium alginate solution being 0.2 to 0.5:1; 3) Mixing calcium chloride with water to obtain a calcium chloride aqueous solution, wherein the mass ratio of calcium chloride to water is (0.02-0.04):1; 4) dropping the seaweed mixed solution mixed with the water-soluble organic liquid in step 2) into the calcium chloride aqueous solution. At this point, the sodium alginate at the interface between the liquid seaweed mixed solution and the calcium chloride aqueous solution reacts rapidly with the calcium chloride to solidify into calcium alginate. The formed outer layer of calcium alginate prevents further reaction, ultimately forming calcium alginate microspheres in the calcium chloride aqueous solution. The outer layer of the calcium alginate microspheres is the formed calcium alginate, and the inner layer is a mixed solution of the water-soluble organic liquid and the sodium alginate solution. 5) After the calcium alginate microspheres are prepared, they are immediately removed from the mixed solution and placed in the air to prevent the calcium alginate shell from becoming too thick; 6) Mixing sodium silicate and water in a mass ratio of 0.03:1 and stirring until completely dissolved to obtain a sodium silicate aqueous solution; 7) After calcium alginate microspheres are uniformly mixed into the sodium silicate aqueous solution, an inorganic temperature-sensitive dynamic phase change fire extinguishing gel material is obtained, wherein the mass ratio of calcium alginate microspheres to sodium silicate solution is 1: (5-20).

2. The method for preparing an inorganic temperature-sensitive dynamic phase-change fire-proofing gel material according to claim 1, characterized in that: Acidic reagents include ammonium sulfate, ammonium chloride, hydrochloric acid, oxalic acid, phosphoric acid, hydrofluoric acid, lactic acid, benzoic acid, acetic acid, formic acid or citric acid; the ratio of the acidic reagent is determined according to the pH value of the acidic substance dissolved in water, ensuring that the pH value of the solution after the acidic reagent reacts with sodium silicate to form a gel is 6-9. The stronger the acidic reagent, the less amount is added. The specific value needs to be determined according to the ratio of calcium alginate microspheres to sodium silicate solution and the hydrogen ion concentration of various acidic substances dissolved in water.

3. The method for preparing an inorganic temperature-sensitive dynamic phase-change fire-proofing gel material according to claim 1, characterized in that: The boiling point of the water-soluble organic liquid is determined based on the self-heating critical temperature of the coal from the slow oxidation stage to the rapid heating stage, which is less than 60°C for lignite, less than 70°C for bituminous coal, and less than 80°C for anthracite. The water-soluble organic liquid is wrapped in the calcium alginate microspheres and will break through the calcium alginate microspheres when the boiling point of the water-soluble organic liquid is reached.

4. The method for preparing an inorganic temperature-sensitive dynamic phase-change fire-proofing gel material according to claim 1, characterized in that: The water-soluble organic liquid includes perfluorohexanone, trifluoroacetic acid, tetrahydrofuran, ethylene glycol dimethyl ether, acetonitrile or isopropyl alcohol.

5. The method for preparing an inorganic temperature-sensitive dynamic phase-change fire-proofing gel material according to claim 1, characterized in that: The mass concentration of calcium chloride solution is 2%-4%.

6. The method for preparing an inorganic temperature-sensitive dynamic phase-change fire-proofing gel material according to claim 1, characterized in that: The mixed solution of sodium alginate, acidic reagent and water-soluble organic liquid is dropped at a rate of 40-90 drops / min.

7. The method for preparing an inorganic temperature-sensitive dynamic phase-change fire-proofing gel material according to claim 6, characterized in that: The diameter of the generated calcium alginate microspheres is 500 μm to 1500 μm. Since the sodium silicate solution is viscous, it can also protect the calcium alginate microspheres from breaking during the grouting process.

8. An inorganic temperature-sensitive dynamic phase-change fire-proof gel material prepared according to the method for preparing an inorganic temperature-sensitive dynamic phase-change fire-proof gel material according to any one of claims 1 to 7.

9. An application of the inorganic temperature-sensitive dynamic phase-change fire-proofing gel material according to claim 8, characterized in that: The inorganic temperature-sensitive dynamic phase-change fire-proofing and extinguishing gel material is sprayed into the goaf and flows through all the remaining coal, so that the inorganic temperature-sensitive dynamic phase-change fire-proofing and extinguishing gel material flows through all the remaining coal and covers it. When the remaining coal area in the goaf is smoldering and a high-temperature area appears, that is, when the coal temperature reaches the critical temperature for turning to the rapid oxidation stage, the water-soluble organic liquid wrapped in the calcium alginate microspheres reaches the boiling point and vaporizes to break through the calcium alginate microspheres, releasing an acidic reagent aqueous solution to react with the sodium silicate solution to form a viscous silica colloid. The formed inorganic temperature-sensitive phase-change gel adheres to the high-temperature area, realizing the targeted identification and retention of high-temperature points in the fire area, and achieving long-term inhibition of low-temperature oxidation of coal and high-temperature flame retardant effect.

10. An application of the inorganic temperature-sensitive dynamic phase-change fire-proofing gel material according to claim 8, characterized in that: Spray the inorganic temperature-sensitive dynamic phase-change fire-proof gel material upstream of the suspected high-temperature area in the goaf, so that when the inorganic temperature-sensitive dynamic phase-change fire-proof gel material flows through the suspected high-temperature area, if the temperature of the suspected high-temperature area reaches the phase change temperature of the inorganic temperature-sensitive dynamic phase-change fire-proof gel material, the solid microcapsules in the inorganic temperature-sensitive dynamic phase-change fire-proof gel material will melt, releasing acidic salts to react with sodium silicate in the suspension to form a viscous silica colloid, the fluidity of which is weakened, and it accumulates at high temperatures, thereby completing the rapid identification and retention of the truly high-temperature area.

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