A mine fire prevention and extinguishing gel based on temperature-controlled release and its preparation method

Abstract

The present invention discloses a mine fire prevention and extinguishing gel based on temperature-controlled release and its preparation method, belonging to the technical field of fire prevention and extinguishing materials. The mine fire prevention and extinguishing gel includes a sodium silicate solution and microcapsules. The microcapsules include a core composed of an acidic reagent and a capsule wall coated outside the core. The core is an acidic reagent, and the capsule wall is a copolymer of gelatin and polysaccharide. When the mine fire prevention and extinguishing gel flows through a suspected high-temperature area, if the gel encounters a real high-temperature area, the microcapsule wall material in the mine fire prevention and extinguishing gel melts, and the acidic substance wrapped by the wall material undergoes a phase change with the sodium silicate solution to generate a silicate gel. The formed silicate gel increases in viscosity, weakens in fluidity, and accumulates at the high-temperature location, completing the identification and residence of the real high-temperature area. It solves the problems of the traditional temperature-sensitive phase change gel having too high an initial viscosity before phase change, losing too much water during phase change, and slow gel formation, realizes the targeted identification and residence of high-temperature points in the fire area, and the material is non-toxic and has a low cost, with broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of fire prevention and extinguishing materials, mainly relates to fire prevention and extinguishing materials and their preparation methods, and specifically relates to a mine fire prevention and extinguishing gel based on temperature-controlled release and its preparation method. 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 huge threat to the life safety of underground workers and equipment safety. 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 collapse of the void areas in the mined-out area of the mine provide a large number of air leakage channels for the residual coal in the mined-out area, resulting in the mined-out area becoming the area most prone to coal spontaneous combustion in coal mines, and 60% of spontaneous combustion fires occur in the mined-out area. 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 according to the fire area temperature. Summary of the Invention

[0004] In order to solve the deficiencies of the prior art, the present invention provides a mine fire prevention and extinguishing gel based on temperature-controlled release and its preparation method. The prepared gel material is initially a liquid with very good fluidity. When passing through the high-temperature points in the fire area, the microcapsules rupture, resulting in an increase in gel viscosity, achieving targeted identification and residence of the high-temperature points in the fire area. Moreover, the material is non-toxic, has a low cost, and has broad application prospects.

[0005] To achieve the above technical objectives, the present invention discloses a preparation method of a mine fire prevention and extinguishing gel based on temperature-controlled release. First, microcapsules are prepared by the complex coacervation method. The microcapsules have a structure of a wall material wrapping a core material. Then, the microcapsules are added to a sodium silicate solution to form a suspension; at room temperature, the core material of the microcapsules in the suspension is separated from the sodium silicate solution substrate, and the two automatically mix and extinguish fire when encountering high temperature;

[0006] The steps are as follows:

[0007] S1. Prepare a gelatin solution and a polysaccharide solution using solid polysaccharide and gelatin respectively, mix them evenly to obtain a wall material solution; the mass ratio of the solid polysaccharide to the gelatin is 1:6 to 1:2, the concentration of the prepared gelatin is 1 to 3 wt%, the solvent amounts of the prepared polysaccharide solution and the gelatin solution are the same, and the concentration ratio is determined according to this mass ratio;

[0008] S2. Add an acidic substance in the form of solid particles to the wall material solution, and the mass ratio of the acidic substance to the total amount of the solid polysaccharide and the gelatin used in preparing the wall material solution in S1 is 0.75:1 to 1.2:1; after homogenization, adjust the pH value of the wall material solution to 3.6 to 4.4, and react to precipitate a colloid to wrap the acidic substance as the core material, and a polymer emulsion is obtained after adjusting the pH value;

[0009] S3. Add an aqueous solution of a curing agent to the polymer emulsion for cross-linking and curing. Since the polysaccharide and the gelatin carry opposite charges, the gelatin coagulates out of the solution, thereby wrapping the acidic substance as the core material. After freeze-drying, granular microcapsules can be obtained; the curing agent is a 35% aqueous formaldehyde solution, and the dosage ratio of the acidic substance to the 35% aqueous formaldehyde solution is 1:6 to 1:15;

[0010] S4. Add the microcapsules to a 10 wt% sodium silicate solution and mix evenly to obtain the mine fire prevention and extinguishing gel based on temperature-controlled release.

[0011] Further, in step S1, the mass ratio of the polysaccharide to the gelatin is preferably 1:3.

[0012] Further, in step S2, the rotation speed of adding the acidic substance to the wall material solution for homogenization is 600 r / min to 1200 r / min, and the homogenization time is 5 min to 8 min.

[0013] Further, the acidic substance includes one or more of acetic acid, lactic acid, ammonium chloride, ammonium sulfate, sodium bisulfate, and ammonium bisulfate aqueous solutions; the polysaccharide includes at least one of gum arabic, carboxymethyl cellulose, sodium alginate, agarose, cyclodextrin, or starch.

[0014] Further, the temperature for adjusting the pH value is 30 °C to 60 °C, and the stirring time for adjustment is 30 min to 40 min.

[0015] Further, the time for adding the aqueous solution of the curing agent to the polymer emulsion for cross-linking and curing is 30 min to 50 min.

[0016] Further, the temperature for freeze-drying is -40 °C to -50 °C, and the freeze-drying time is 10 h to 16 h.

[0017] A mine fire prevention and extinguishing gel based on temperature-controlled release prepared by the preparation method of the mine fire prevention and extinguishing gel based on temperature-controlled release described in claim 1.

[0018] Furthermore, it is composed of a sodium silicate solution and microcapsules. The microcapsules include a core composed of an acidic reagent and a capsule wall coated on the outside of the core. The core is an acidic substance, and the wall material of the capsule wall is a copolymer of gelatin and polysaccharide. The wall material of the microcapsule capsule wall melts at high temperature to release the core to react with the sodium silicate solution to form a gel.

[0019] An application of the mine fire prevention and extinguishing gel based on temperature-controlled release described in claim 8: Spraying or injecting the mine fire prevention and extinguishing gel based on temperature-controlled release upstream of the suspected high-temperature area in the goaf, so that the mine fire prevention and extinguishing gel flows through the suspected high-temperature area. If the gel encounters a real high-temperature area, the wall material of the microcapsules in the mine fire prevention and extinguishing gel melts, and the acidic substance wrapped by the wall material reacts with the sodium silicate solution to generate a silicic acid gel. The viscosity of the formed silicic acid gel increases, the fluidity weakens, and it accumulates at the high temperature, completing the identification and residence of the real high-temperature area.

[0020] Beneficial effects: Compared with the prior art, the inorganic temperature-sensitive phase-change gel material for preventing coal spontaneous combustion provided by the present invention, its preparation method and application have the following specific advantages:

[0021] The inorganic temperature-sensitive 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 fire-resistant 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 in the present invention, the sodium silicate aqueous solution forms a silicic acid gel, which can realize that the initial state of the gel material is a liquid with good fluidity, and the viscosity of the gel will increase when passing through the high-temperature point of the fire area, realizing the targeted residence of the fire area. The microcapsules have a particle size of about dozens of micrometers, are small in volume, can be evenly distributed in the gaps of coal blocks, have a wide coverage range, and can stably form a gel at a smaller scale. Compared with the organic temperature-sensitive phase-change gel, the inorganic sodium silicate gel provided by the present invention has a fast gel-forming speed, good initial fluidity, a low price, and is safe and environmentally friendly. Specific implementation

[0022] The following further describes the embodiments of the present invention:

[0023] The present invention discloses a preparation method of a mine fire prevention and extinguishing gel based on temperature-controlled release. First, microcapsules are prepared by the complex coacervation method. The microcapsules have a structure of a wall material wrapping a core material, and then the microcapsules are added to a sodium silicate solution to form a suspension; at room temperature, the core material of the microcapsules in the suspension is separated from the sodium silicate solution substrate, and the two automatically mix and extinguish fire when encountering high temperature;

[0024] The steps are as follows:

[0025] S1. Prepare a gelatin solution and a polysaccharide solution respectively using solid polysaccharide and gelatin, mix them evenly to obtain a wall material solution. The mass ratio of the solid polysaccharide to gelatin is 1:6 - 1:2. The concentration of the prepared gelatin is 1 - 3 wt%. The solvent amounts of the prepared polysaccharide solution and gelatin solution are the same, and the concentration ratio is determined based on this mass ratio. The mass ratio of the polysaccharide to gelatin is preferably 1:3.

[0026] The acidic substances include one or more of acetic acid, lactic acid, ammonium chloride, ammonium sulfate, sodium bisulfate, and ammonium bisulfate aqueous solution. The polysaccharide includes at least one of gum arabic, carboxymethyl cellulose, sodium alginate, agarose, cyclodextrin, or starch.

[0027] S2. Add solid particulate acidic substances to the wall material solution. The mass ratio of the acidic substances to the total amount of the solid polysaccharide and gelatin used to prepare the wall material solution in S1 is 0.75:1 - 1.2:1. After homogenization, adjust the pH value of the wall material solution to 3.6 - 4.4, the temperature to 30°C - 60°C, adjust the stirring time to 30 min - 40 min, and react to precipitate a colloid to wrap the acidic substances as the core material, obtaining a polymer emulsion after adjusting the pH value. The rotation speed for homogenizing the addition of acidic substances to the wall material solution is 600 r / min - 1200 r / min, and the homogenization time is 5 min - 8 min.

[0028] S3. Add an aqueous solution of a curing agent to the polymer emulsion for cross - linking and curing. The cross - linking and curing time is 30 min - 50 min. Since the polysaccharide and gelatin carry opposite charges, the gelatin coagulates out of the solution, thus wrapping the acidic substances as the core material. After freeze - drying, granular microcapsules can be obtained. The temperature is - 40°C - 50°C, and the freeze - drying time is 10 h - 16 h. The curing agent is a 35% aqueous formaldehyde solution, and the dosage ratio of the acidic substances to the 35% aqueous formaldehyde solution is 1:6 - 1:15.

[0029] S4. Add the microcapsules to a sodium silicate solution with a concentration of 10 wt% to obtain the mine fire - prevention and extinguishing gel based on temperature - controlled release.

[0030] It is composed of a sodium silicate solution and microcapsules. The microcapsules include a core composed of acidic reagents and a capsule wall coated on the outside of the core. Among them, the core is an acidic substance, and the wall material of the capsule wall is a copolymer of gelatin and polysaccharide. The wall material of the microcapsule capsule wall melts at high temperature to release the core, which reacts with the sodium silicate solution to form a gel.

[0031] Spray or inject a mine fire prevention and extinguishing gel based on temperature-controlled release upstream of the suspected high-temperature area in the goaf, so that the mine fire prevention and extinguishing gel flows through the suspected high-temperature area. If the gel encounters a real high-temperature area, the microcapsule wall material in the mine fire prevention and extinguishing gel melts, and the acidic substance wrapped by the wall material undergoes a phase change with the sodium silicate solution to generate silica gel. The viscosity of the formed silica gel increases, the fluidity weakens, and it accumulates at the high-temperature location, completing the identification and residence of the real high-temperature area. Example

[0032] A mine fire prevention and extinguishing gel based on temperature-controlled release disclosed by the present invention has the following preparation method:

[0033] Weigh 1.5 g of gelatin, soak it in a little purified water. After it swells, add 50 ml of purified water and stir to dissolve it in a water bath at 60 °C to prepare a gelatin solution with a concentration of 3 wt%. Dry the gum arabic in an oven at 80 °C for 1 h, and take 0.5 g of the dried gum arabic and add 50 ml of purified water to make a solution with a concentration of 1 wt%. Add 2 g of ammonium chloride to the gelatin solution, stir to form an emulsion, then add the gum arabic solution to it, and stir evenly at a constant temperature of 40 °C with a magnetic stirrer at a stirring speed of 600 r / min, adjust the pH to 4, and continue stirring at a constant temperature for 40 min.

[0034] Add twice the volume of purified water at 30 °C, stir and wait for it to cool naturally to room temperature, then place it in an ice-water bath and stir to cool it below 10 °C. Adjust the pH value of the system to 8 - 9, add 5 ml of 35% formaldehyde aqueous solution to solidify for 30 min. Let it stand for sedimentation, pour off the supernatant, centrifuge, wash it with purified water until there is no aldehyde smell, and place it in a freeze dryer for low-temperature vacuum drying to obtain the required microcapsules.

[0035] Add the microcapsules to the sodium silicate solution to obtain the mine fire prevention and extinguishing gel based on temperature-controlled release. Example

[0036] A mine fire prevention and extinguishing gel based on temperature-controlled release disclosed by the present invention has the following preparation method:

[0037] Weigh 1.5 g of gelatin, soak it in a little purified water. After it swells, add 50 ml of purified water and stir to dissolve it in a water bath at 60 °C to prepare a gelatin solution with a concentration of 3 wt%. Take 0.3 g of sodium alginate as a polysaccharide and add 50 ml of purified water to make a solution with a concentration of 0.6 wt%. Add 1.5 g of ammonium bisulfate to the gelatin solution, stir to form an emulsion, then add the gum arabic solution to it, and stir evenly at a constant temperature of 40 °C with a magnetic stirrer at a stirring speed of 800 r / min, adjust the pH to 4.2, and continue stirring at a constant temperature for 30 min.

[0038] Add twice the volume of purified water at 30 °C, stir and wait for it to cool naturally to room temperature. Place it in an ice-water bath and stir to cool it to below 10 °C. Adjust the pH value of the system to 8-9, add 7 ml of 35% formaldehyde aqueous solution and cure for 350 min. Let it stand for sedimentation, pour off the supernatant, centrifuge, wash with purified water until there is no aldehyde smell, and place it in a freeze dryer for low-temperature vacuum drying to obtain the required microcapsules.

Claims

1. A method for preparing a fire-fighting gel for mining based on temperature-controlled release, characterized in that: First, the microcapsules are prepared by complex coagulation method. The microcapsules are a structure in which the core material is wrapped by the wall material. Then, the microcapsules are added into the sodium silicate solution to form a suspension. At room temperature, the microcapsule core material and the sodium silicate solution in the suspension are separated as substrates. When they encounter high temperature, the two automatically mix and extinguish the fire. Here are the steps: S1. Prepare gelatin solution and polysaccharide solution using solid polysaccharide and gelatin respectively, mix them evenly, and obtain wall material solution; the mass ratio of solid polysaccharide and gelatin is 1:6-1:2, the concentration of prepared gelatin is 1-3wt%, and the amount of solvent in the prepared polysaccharide solution is the same as that in the gelatin solution, and the concentration ratio is determined by this mass ratio; S2, adding a solid granular acidic substance to the wall material solution, wherein the mass ratio of the acidic substance to the total amount of solid polysaccharide and gelatin used in preparing the wall material solution in S1 is 0.75:1-1.2:1; adjusting the pH value of the wall material solution to 3.6-4.4 after homogenization, reacting and precipitating a colloid to encapsulate the acidic substance as the core material, and adjusting the pH value to obtain a polymer emulsion; S3, adding a curing agent aqueous solution to the polymer emulsion for cross-linking and curing. Since the polysaccharide and gelatin have opposite charges, the gelatin condenses from the solution, thereby wrapping the acidic substance as the core material. After freeze-drying, granular microcapsules can be obtained; the curing agent is a 35% formaldehyde aqueous solution, and the ratio of the acidic substance to the 35% formaldehyde aqueous solution is 1:6 to 1:15; S4, adding the microcapsules to a sodium silicate solution with a concentration of 10wt% and mixing them evenly to obtain the mine fire extinguishing gel based on temperature-controlled release; The acidic substance is one or more of acetic acid, lactic acid, ammonium chloride, ammonium sulfate, sodium bisulfate, and ammonium bisulfate; the polysaccharide is at least one of gum arabic, carboxymethyl cellulose, sodium alginate, agarose, cyclodextrin, or starch.

2. The method for preparing a temperature-controlled release-based fire-fighting gel for mining according to claim 1, characterized in that: In step S1, the mass ratio of the polysaccharide to gelatin is 1:

3.

3. The method for preparing a temperature-controlled release-based fire-extinguishing gel for mining according to claim 1, characterized in that: In step S2, the acidic substance is added to the wall material solution for homogenization at a speed of 600 r / min to 1200 r / min, and the homogenization time is 5 min to 8 min.

4. The method for preparing a mine fire extinguishing gel based on temperature-controlled release according to claim 1, characterized in that: The temperature when adjusting the pH value is 30°C to 60°C, and the stirring time is adjusted to 30min to 40min.

5. The method for preparing a temperature-controlled release-based fire-extinguishing gel for mining according to claim 1, characterized in that: The time for adding the curing agent aqueous solution to the polymer emulsion for cross-linking and curing is 30 minutes to 50 minutes.

6. The method for preparing a temperature-controlled release-based fire-fighting gel for mining according to claim 1, characterized in that: The freeze-drying temperature is -40°C to -50°C, and the freeze-drying time is 10h to 16h.