Inorganic thermosensitive phase change gel material for preventing and controlling coal spontaneous combustion, preparation method and application

Abstract

The present invention discloses an inorganic temperature-sensitive phase-change gel material for preventing and controlling coal spontaneous combustion, a preparation method and an application, belonging to the technical field of fire prevention and extinguishing in coal mine gob areas. It includes an aqueous sodium silicate solution and an acidic salt sealed in microcapsules, wherein 30-40 parts of the temperature-sensitive phase-change material shell and 60-70 parts of the acidic salt powder; after heating the phase-change material to the molten state, add acidic salt particles and mix evenly, add gelatin and span 80 and stir evenly, then cool down to obtain a solid product, crush and grind the solid product to obtain solid particles with a particle size of 40-60 mesh, put the solid particles into clear water to wash away the uncoated acidic salt, and dry to obtain microcapsules encapsulating the acidic salt, and add the microcapsules to the sodium silicate solution to obtain an inorganic temperature-sensitive phase-change suspension. This structure is simple and convenient to use, and can achieve the effect of automatic fire extinguishing when laid on the coal that may spontaneously combust.

Description

Technical Field

[0001] The invention belongs to the technical field of preventing and extinguishing fires in goafs of coal mines, and particularly relates to an inorganic temperature-sensitive phase-change gel material for preventing and controlling coal spontaneous combustion, a preparation method and an application thereof. Background Art

[0002] During the coal mining process, more than 90% of mine fires are caused by coal spontaneous combustion. Coal will undergo an oxidation reaction with oxygen in an aerobic environment and accumulate heat, resulting in a slow rise in coal temperature. When the coal temperature exceeds the critical temperature, the coal temperature will rise sharply and spontaneous combustion will occur. Coal spontaneous combustion not only damages coal resources, but also triggers major accidents such as mine fires and gas explosions, posing a great threat to the lives and equipment safety of underground workers. To create a safe mining environment, effective prevention and control measures must be taken against coal spontaneous combustion.

[0003] The caving voids and separated layer fissures formed after the caving of the void area in the goaf of the mine provide a large number of air leakage channels for the residual coal in the goaf, resulting in the goaf becoming the area most prone to coal spontaneous combustion in coal mines, and 60% of spontaneous combustion fires occur in the goaf. For mine fires or coalfield fires, coal spontaneous combustion does not develop evenly, but there are high-temperature points. The high-temperature points in the fire area may form and develop anywhere in the fire area, and the high-temperature points gradually change with coal mining and fissure air leakage in the coal mine; if the high-temperature points in the fire area are not effectively prevented and controlled, they will eventually evolve into coal spontaneous combustion accidents. The complex underground environment provides good conditions for coal spontaneous combustion and increases the difficulty of detecting the location of high-temperature points. Therefore, there is an urgent need to develop a material that can automatically identify high-temperature points in the fire area and release and targetedly stay at the fire area temperature in sequence.

[0004] The State Administration of Coal Mine Safety Supervision has issued the "Trial Measures for the Safety Management of Reactive Polymer Materials in Coal Mines", which clearly stipulates that "high-molecular materials formed by strongly corrosive and strongly volatile components shall not be used in coal mines, and high-molecular materials with violent chemical reactions and large heat releases are prohibited from being used in locations directly in contact with coal, and polyurethane foaming materials are prohibited from being used in filling and sealing operations". It can be seen that organic temperature-sensitive gels belong to high-molecular materials, and their applications are restricted in many ways. Inorganic gels do not have temperature-sensitive properties. Therefore, it is very necessary to find an environmentally friendly, non-toxic method for preventing and controlling coal spontaneous combustion with good prevention and control effects and reasonable economy. Summary of the Invention

[0005] In order to solve the deficiencies of the prior art, the invention provides an inorganic temperature-sensitive phase-change gel material for preventing and controlling coal spontaneous combustion, a preparation method and an application thereof. The initial state of the gel material is a liquid with good fluidity. When passing through the high-temperature points in the fire area, the gel viscosity will increase to achieve targeted residence in the fire area. The components used will not pollute the environment, are non-toxic and harmless, have a wide source, and the cost is controllable.

[0006] To solve the above technical problems, the present invention provides a preparation method of an inorganic temperature-sensitive phase-change gel material for preventing and controlling coal spontaneous combustion. The inorganic temperature-sensitive phase-change gel material is a sodium silicate solution in which a large number of temperature-sensitive microcapsules are suspended. At room temperature, the core material of the temperature-sensitive microcapsules in the suspension is separated from the sodium silicate solution substrate and does not contact. When encountering high temperature, the two automatically mix to extinguish the fire;

[0007] The steps are as follows:

[0008] S1. Heat the temperature-sensitive phase-change material to a molten state;

[0009] S2. Under the condition of an inert gas atmosphere, gradually add acidic salt powder to the molten temperature-sensitive phase-change material in portions and keep stirring, so that the acidic salt powder particles are evenly dispersed in the molten temperature-sensitive phase-change material. To ensure the molten state of the temperature-sensitive phase-change material, it is necessary to carry out in an environment where the temperature is 4°C to 10°C higher than the melting point of the phase-change material; the weight ratio of the temperature-sensitive phase-change material to the added acidic salt powder is: 30 to 40 parts of the temperature-sensitive phase-change material, 60 to 70 parts of the acidic salt powder. The temperature-sensitive phase-change material is an inorganic hydrophobic phase temperature-sensitive material, and the acidity of the acidic salt powder is greater than that of silicic acid;

[0010] S3. Add gelatin and span 80 as emulsifiers to the molten temperature-sensitive phase-change material mixed with acidic salt powder, stir evenly, and then cool down to obtain a solid product, so that the acidic salt powder is more fully and evenly dispersed in the molten temperature-sensitive phase-change material; the added amount is 0.3 to 0.8 parts of gelatin and 0.3 to 0.8 parts of span 80;

[0011] S4. Crush and grind the solid product into solid particles with a particle size of 40 to 60 mesh. The solid particles are temperature-sensitive microcapsules. The temperature-sensitive microcapsules are structures in which the temperature-sensitive phase-change material wraps the inorganic salt inhibitor. Due to the preparation process, some temperature-sensitive microcapsules cannot ensure that the temperature-sensitive phase-change material completely wraps the inorganic salt inhibitor. Therefore, the crushed and ground solid particles are placed in cold water for 5 to 10 minutes to wash away the acidic salt powder that is not completely wrapped by the temperature-sensitive phase-change material and the acidic salt powder leaked during crushing, and then dried for standby;

[0012] S5. Add the temperature-sensitive microcapsules to the sodium silicate solution and mix evenly to obtain an inorganic temperature-sensitive phase-change suspension. The mass concentration of the sodium silicate solution is 2% to 4%, and the mass ratio of the temperature-sensitive microcapsules to the sodium silicate solution is 1:5 to 1:10. The inorganic temperature-sensitive phase-change suspension is the inorganic temperature-sensitive phase-change gel material.

[0013] Further, the inorganic hydrophobic phase thermosensitive material has hydrophobicity and is one or a mixture of more of 70# chlorinated paraffin, 52# chlorinated paraffin, polyethylene glycol, polyvinyl chloride, ethyl cellulose, and pentaerythritol stearate; the inorganic hydrophobic phase thermosensitive material is determined according to the required melting point, and the melting point should be determined according to the self-heating critical temperature of the coal from the slow oxidation stage to the rapid oxidation heating stage, less than 65 °C for lignite, less than 70 °C for bituminous coal, and less than 80 °C for anthracite.

[0014] Preferably, the further inorganic hydrophobic phase thermosensitive material is a mixture of 70# chlorinated paraffin and 52# chlorinated paraffin in a mass ratio of 5:1.

[0015] Further, the inert gas includes one of nitrogen, helium, and carbon dioxide;

[0016] Further, the acidic salt powder includes one or more of ammonium chloride, ammonium sulfate, sodium bisulfate, and ammonium bisulfate, and the particle size of the acidic salt powder is 80-120 mesh.

[0017] Further, the modulus of sodium silicate is 2-3.

[0018] Further, a thickener is added to the sodium silicate solution as needed to improve the adhesion viscosity of the finished inorganic thermosensitive phase change gel material, and the thickener includes sodium polyacrylate and polyacrylamide.

[0019] An inorganic thermosensitive phase change gel material for preventing coal spontaneous combustion prepared by a preparation method of an inorganic thermosensitive phase change gel material for preventing coal spontaneous combustion.

[0020] An application of an inorganic thermosensitive phase change gel material for preventing coal spontaneous combustion. When there is a suspected natural fire tendency in the goaf, an inorganic thermosensitive phase change suspension is sprayed or injected upstream of the suspected high-temperature area, so that the inorganic thermosensitive phase change suspension flows through and covers the suspected high-temperature area. When the temperature of the suspected high-temperature area reaches the phase change temperature of the inorganic thermosensitive phase change suspension, the thermosensitive microcapsules in the inorganic thermosensitive phase change suspension melt, and the released acidic salt reacts with the sodium silicate in the suspension to form a viscous silicic acid colloid, and the fluidity weakens. And because the closer to the high-temperature area, the more it melts at the high-temperature area, so that the silicic acid colloid accumulates at the high-temperature area, completing the rapid identification and residence of the true high-temperature area, covering the high-temperature point with the gel to isolate oxygen and preventing the sprayed area from continuing to heat up.

[0021] Further, when the coal seam dip angle is greater than 25 degrees, a thickener is added to the sodium silicate solution to improve the viscosity of the inorganic thermosensitive phase change suspension.

[0022] Beneficial effects

[0023] Compared with the prior art, the inorganic thermosensitive phase change gel material for preventing coal spontaneous combustion provided by the present invention, its preparation method and application have the following specific advantages:

[0024] The inorganic thermosensitive phase change gel material for preventing coal spontaneous combustion of the present invention is non-toxic and harmless, does not pollute the environment, has a wide source, a low and controllable price, and a simple and efficient manufacturing process. Sodium silicate gel is a water-soluble silicate, which can be used as an adhesive for cardboard, wood, and refractory materials, making glass more refractory and corrosion-resistant in glass manufacturing, and can also be used to manufacture environmentally friendly biodegradable materials, and can react with acidic substances to form silicic acid gel. Through the temperature-controlled release of microcapsules, the aqueous solution of sodium silicate forms silicic acid gel in the present invention, which can make the initial state of the gel material a liquid with good fluidity, and the gel viscosity will increase when passing through the high-temperature point of the fire area, realizing the targeted residence in the fire area. The microcapsules have a particle size of about dozens of micrometers, are small in size, can be evenly distributed in the gaps of coal blocks, have a wide coverage range, and can stably form gel at a smaller scale. Compared with the organic thermosensitive phase change gel, the inorganic sodium silicate gel provided by the present invention has a fast gelation speed, good initial fluidity, low price, and is safe and environmentally friendly. Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the preparation process of the inorganic thermosensitive phase change gel material recorded in the present invention.

[0026] Figure 2 It is a schematic diagram of the principle of the inorganic thermosensitive phase change gel material of the present invention changing from a suspension to a phase change gel.

[0027] Figure 3 It is a physical picture of the thermosensitive microcapsules in the inorganic thermosensitive phase change gel material of the present invention. Detailed Embodiments

[0028] The following further describes the embodiments of the present invention with reference to the drawings.

[0029] As Figure 1 shown, the preparation method of the inorganic thermosensitive phase change gel material for preventing coal spontaneous combustion of the present invention, the inorganic thermosensitive phase change gel material is a sodium silicate solution in which a large number of thermosensitive microcapsules are suspended. At normal temperature, the core material of the thermosensitive microcapsules in the suspension is separated from the sodium silicate solution substrate and does not contact. When encountering high temperature, the two automatically mix to extinguish the fire;

[0030] The steps are as follows:

[0031] S1. Heat the thermosensitive phase change material to a molten state;

[0032] S2. Sequentially and gradually add acidic salt powder to the molten temperature-sensitive phase change material under an inert gas atmosphere and keep stirring to form a mixed liquid. To ensure the molten state of the temperature-sensitive phase change material, it is necessary to carry out the operation in an environment where the temperature is 4°C to 10°C higher than the melting point of the phase change material. The weight ratio of the temperature-sensitive phase change material to the added acidic salt powder is as follows: 30 to 40 parts of the temperature-sensitive phase change material and 60 to 70 parts of the acidic salt powder. The temperature-sensitive phase change material is an inorganic hydrophobic temperature-sensitive material, and the acidity of the acidic salt powder is greater than that of silicic acid.

[0033] S3. Add gelatin and Span 80 to the mixed liquid, stir evenly, and then cool down to obtain a solid product. The added amounts are 0.3 to 0.8 parts of gelatin and 0.3 to 0.8 parts of Span 80.

[0034] S4. Crush and grind the solid product into solid particles with a particle size of 40 to 60 mesh. The solid particles are temperature-sensitive microcapsules, and the temperature-sensitive microcapsules have a structure in which the temperature-sensitive phase change material wraps the inorganic salt inhibitor. Due to the preparation process, some temperature-sensitive microcapsules cannot ensure that the temperature-sensitive phase change material completely wraps the inorganic salt inhibitor. Therefore, place the crushed and ground solid particles in cold water for 5 to 10 minutes to wash away the acidic salt powder that is not completely wrapped by the temperature-sensitive phase change material and the acidic salt powder leaked during crushing, and dry them for later use.

[0035] S5. Add the temperature-sensitive microcapsules to the sodium silicate solution to obtain an inorganic temperature-sensitive phase change suspension. The mass concentration of the sodium silicate solution is 2% to 4%, and the mass ratio of the temperature-sensitive microcapsules to the sodium silicate solution is 1:5 to 1:10. The inorganic temperature-sensitive phase change suspension is an inorganic temperature-sensitive phase change gel material, as shown in Figure 3 specifically.

[0036] When there is a suspected natural fire tendency in the goaf, spray or inject the inorganic temperature-sensitive phase change suspension upstream of the suspected high-temperature area, so that the inorganic temperature-sensitive phase change suspension flows through and covers the suspected high-temperature area. When the temperature of the suspected high-temperature area reaches the phase change temperature of the inorganic temperature-sensitive phase change suspension, the wall material of the temperature-sensitive microcapsules in the inorganic temperature-sensitive phase change suspension melts, and the released acidic salt reacts with the sodium silicate in the suspension to form a viscous silicic acid colloid, as Figure 2 shown, the fluidity weakens, and the closer to the high-temperature area, the more it melts at the high-temperature area. Thus, the silicic acid colloid accumulates at the high-temperature area, completing the rapid identification and residence of the true high-temperature area, covering the high-temperature point with the gel to isolate oxygen and prevent the sprayed area from continuing to heat up. When the coal seam dip angle is greater than 25 degrees, a thickening agent is added to the sodium silicate solution to increase the viscosity of the inorganic temperature-sensitive phase change suspension.

[0037] Example 1

[0038] For bituminous coal, its self-heating critical temperature is about 70°C. Therefore, a phase change gel with a phase change temperature below 70°C needs to be prepared to prevent the rapid oxidation of lignite.

[0039] An inorganic thermosensitive phase change gel material for preventing and controlling coal spontaneous combustion. Weigh 24 parts of polyethylene glycol 20000 and 16 parts of pentaerythritol stearate, mix them in a beaker, and place the beaker in a water bath at 70 °C and heat until it reaches the molten state and stir evenly to obtain the wall material mixed liquid. Under the environment of nitrogen, gradually add 60 parts of 100-mesh ammonium chloride powder to the wall material mixed liquid in portions and continuously stir. After stirring evenly, add gelatin and span 80 to the mixed liquid, stir evenly, and then cool down to obtain a solid product. Crush and grind the prepared solid product to obtain thermosensitive microcapsule particles with a particle size of 50 mesh, place the particles in cold water for 5 - 10 minutes to wash off the acidic salt powder on the surface, filter and dry to obtain thermosensitive microcapsules encapsulating acidic salts. Add the prepared microcapsules to 500 parts of a sodium silicate solution with a mass fraction of 3% to obtain an inorganic thermosensitive phase change suspension;

[0040] Inject the above-mentioned inorganic thermosensitive phase change suspension into the gob area through a grouting pipeline. When the suspension reaches the high-temperature point of coal spontaneous combustion, when the temperature reaches above 63 °C, the microcapsule wall material melts, releasing ammonium chloride to react with sodium silicate to form an inorganic thermosensitive phase change gel, and the viscosity of the generated silicic acid gel increases and can remain in the high-temperature point of the gob area for a long time.

[0041] Example 2

[0042] For anthracite, its self-heating critical temperature is about 85 °C. Therefore, a phase change gel with a phase change temperature below 85 °C needs to be prepared to prevent the rapid oxidation of lignite.

[0043] An inorganic thermosensitive phase change gel material for preventing and controlling coal spontaneous combustion. Weigh 50 parts of chlorinated paraffin 70# and 8 parts of chlorinated paraffin 52#, mix them in a beaker, and place the beaker in a water bath at 80 °C and heat until it reaches the molten state and stir evenly to obtain the wall material mixed liquid. Under the environment of carbon dioxide, gradually add 170 parts of 100-mesh ammonium sulfate powder to the wall material mixed liquid in portions and continuously stir. After stirring evenly, add gelatin and span 80 to the mixed liquid, stir evenly, and then cool down to obtain a solid product. Crush and grind the prepared solid product to obtain particles with a particle size of 60 mesh, place the particles in cold water for 5 - 10 minutes to wash off the acidic salt powder on the surface, filter and dry to obtain thermosensitive microcapsules encapsulating acidic salts. Add the prepared microcapsules to 1500 parts of a sodium silicate solution with a mass fraction of 3.5% to obtain an inorganic thermosensitive phase change suspension;

[0044] Inject the above-mentioned inorganic thermosensitive phase change suspension into the gob area through a grouting pipeline. When the suspension reaches the high-temperature point of coal spontaneous combustion, when the temperature reaches above 75 °C, the microcapsule wall material melts, releasing ammonium sulfate to react with sodium silicate to form an inorganic thermosensitive phase change gel, and the viscosity of the generated silicic acid gel increases and can remain in the high-temperature point of the gob area for a long time.

[0045] Example 3

[0046] For lignite, its self-heating critical temperature is about 65 °C. Therefore, a phase change gel with a phase change temperature below 65 °C needs to be prepared to prevent the rapid oxidation of lignite.

[0047] An inorganic thermosensitive phase change gel material for preventing coal spontaneous combustion. Weigh 40 parts of 70# chlorinated paraffin and 18 parts of 52# chlorinated paraffin, mix them in a beaker, and place the beaker in a water bath at 70 °C and heat until it reaches the molten state and stir evenly to obtain the wall material mixed liquid. Under the environment of carbon dioxide, gradually add 170 parts of 100-mesh ammonium sulfate powder to the wall material mixed liquid and keep stirring. After stirring evenly, add gelatin and Span 80 to the mixed liquid, stir evenly, and then cool down to obtain a solid product. Crush and grind the prepared solid product to obtain particles with a particle size of 40 mesh, place the particles in cold water for 5 - 10 minutes to wash off the acidic salt powder on the surface, filter and dry them to obtain thermosensitive microcapsules encapsulating acidic salts. Add the prepared microcapsules to 1500 parts of a sodium silicate solution with a mass fraction of 2.5% to obtain an inorganic thermosensitive phase change suspension; add 100 parts of a 2% polyacrylamide solution to the inorganic thermosensitive phase change suspension;

[0048] Inject the above-mentioned inorganic thermosensitive phase change suspension into the gob area through the grouting pipeline. When the suspension reaches the high-temperature point of coal spontaneous combustion and the temperature reaches above 63 °C, the wall material of the microcapsules melts, releasing ammonium sulfate to react with sodium silicate to form an inorganic thermosensitive phase change gel. The viscosity of the generated silicic acid gel increases and can stay in the high-temperature point of the gob area for a long time.

Claims

1. A method for preparing an inorganic temperature-sensitive phase change gel material for preventing and controlling spontaneous combustion of coal, characterized in that: The inorganic thermosensitive phase change gel material is a large number of thermosensitive microcapsules suspended in a sodium silicate solution. At room temperature, the thermosensitive microcapsule core material in the suspension is separated from the sodium silicate solution substrate and does not contact each other. When encountering high temperature, the two automatically mix and extinguish the fire. Here are the steps: S1, heating the temperature-sensitive phase change material to a molten state; S2. In an inert gas atmosphere, gradually add acid salt powder to the molten temperature-sensitive phase change material and keep stirring, so that the acid salt powder particles are evenly dispersed in the molten temperature-sensitive phase change material. The stirring process needs to ensure that the heating temperature is 4°C to 10°C higher than the melting point of the phase change material to ensure the molten state of the temperature-sensitive phase change material. The weight ratio of the thermosensitive phase change material to the added acidic salt powder is: 30-40 parts of the thermosensitive phase change material and 60-70 parts of the acidic salt powder; S3, add gelatin and Span 80 as emulsifiers to the molten state temperature-sensitive phase change material of the mixed acidic salt powder, stir evenly, and then cool to obtain a solid product, so that the acidic salt powder is more fully and evenly dispersed in the molten state temperature-sensitive phase change material; the amount added is 0.3-0.8 parts of gelatin and 0.3-0.8 parts of Span 80; S4, crushing and grinding the solid product into solid particles with a particle size of 40 to 60 mesh, the solid particles are the thermosensitive microcapsules, the thermosensitive microcapsules are the structure of the thermosensitive phase change material encapsulating the inorganic salt inhibitor, due to the preparation process, some thermosensitive microcapsules cannot ensure that the thermosensitive phase change material completely encapsulates the inorganic salt inhibitor, so the thermosensitive microcapsules are placed in cold water for 5 to 10 minutes to wash away the acidic salt powder that is not completely encapsulated by the thermosensitive phase change material and the acidic salt powder leaked during crushing, and then dried for use; S5, adding the thermosensitive microcapsules to the sodium silicate solution and mixing them evenly to obtain an inorganic thermosensitive phase change suspension, wherein the mass concentration of the sodium silicate solution is 2% to 4%, the mass ratio of the thermosensitive microcapsules to the sodium silicate solution is 1:5 to 1:10, and the inorganic thermosensitive phase change suspension is an inorganic thermosensitive phase change gel material; The acidity of the acidic salt powder is greater than that of silicic acid, and includes one or more of ammonium chloride, ammonium sulfate, sodium bisulfate, and ammonium bisulfate; the temperature-sensitive phase change material is a hydrophobic material, and is a mixture of one or more of 70# chlorinated paraffin, 52# chlorinated paraffin, polyethylene glycol, polyvinyl chloride, ethyl cellulose, and pentaerythritol stearate; and the melting point of the temperature-sensitive phase change material is determined according to the self-heating critical temperature of coal from the slow oxidation stage to the rapid oxidation temperature rise stage, which is less than 65°C for lignite, less than 70°C for bituminous coal, and less than 80°C for anthracite.

2. The method for preparing an inorganic temperature-sensitive phase change gel material for preventing and controlling spontaneous combustion of coal according to claim 1, characterized in that: The temperature-sensitive phase change material is a mixture of 70# chlorinated paraffin and 52# chlorinated paraffin in a mass ratio of 5:

1.

3. The method for preparing an inorganic temperature-sensitive phase change gel material for preventing and controlling spontaneous combustion of coal according to claim 1, characterized in that: The inert gas is one of nitrogen, helium and carbon dioxide.

4. The method for preparing an inorganic temperature-sensitive phase change gel material for preventing and controlling spontaneous combustion of coal according to claim 1, characterized in that: The particle size of the acid salt powder is 80~120 mesh.

5. The method for preparing an inorganic temperature-sensitive phase change gel material for preventing and controlling spontaneous combustion of coal according to claim 1, characterized in that: The modulus of sodium silicate is 2~3.

6. The method for preparing an inorganic temperature-sensitive phase change gel material for preventing and controlling spontaneous combustion of coal according to claim 1, characterized in that: When the inclination of the coal seam is greater than 25 degrees, a thickener needs to be added to the sodium silicate solution to increase the viscosity of the inorganic thermosensitive phase change suspension. The thickener is sodium polyacrylate or polyacrylamide.

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