A forest silicic-alumina sol fire extinguishing agent, its preparation method and application

Abstract

The application discloses a forest silicon-aluminum sol fire extinguishing agent, a preparation method and application thereof, and belongs to the technical field of forest fire fighting. The forest silicon-aluminum sol fire extinguishing agent comprises A liquid and B liquid in a weight ratio of 2-30:1. The A liquid comprises the following raw materials in parts by weight: 15-35 parts of silicon sol, 2-20 parts of aluminum sol, 0.01-0.4 parts of sphingosine glue, 1-5 parts of flame retardant, 0.1-0.5 parts of dispersing agent, 0.01-0.3 parts of polysol and 50-70 parts of water. The B liquid comprises the following raw materials in parts by weight: 0.1-2 parts of titanium gluconate and 5-15 parts of water. The application further discloses a preparation method and application of the forest silicon-aluminum sol fire extinguishing agent. The forest silicon-aluminum sol fire extinguishing agent can solve the problems of poor adhesion, poor anti-reignition, complicated components and easy stratified precipitation of the existing gel fire extinguishing agent, can effectively improve the success rate of forest fire fighting and the safety of a fire site, and has good practical value.

Description

Technical Field

[0001] This invention belongs to the field of forest fire fighting technology, specifically relating to a forest-use silica-alumina sol fire extinguishing agent, its preparation method, and its application. Background Technology

[0002] Currently, water-based fire extinguishing agents, foam fire extinguishing agents, and dry powder fire extinguishing agents remain the mainstream fire extinguishing products on the market. However, forest fires are characterized by their suddenness, rapid spread, and complex fighting environments, revealing significant shortcomings in the application of traditional fire extinguishing materials in forest areas. While water is widely available, its high surface tension and tendency to run off result in a very short residence time on sloping vegetation surfaces, making it difficult to provide sustained cooling and isolation protection for combustibles. Although ordinary foam fire extinguishing agents offer good coverage, their slow film-forming speed and limited burning resistance mean that the foam is prone to bursting under high fire temperatures, leading to rapid reignition of any remaining embers. Dry powder fire extinguishing agents have poor adhesion to vegetation, and when used in large quantities, the powder tends to disperse and deposit in the soil, potentially disrupting the micro-environmental balance of the forest ecosystem. Furthermore, post-fire cleanup is extremely difficult.

[0003] In recent years, sol-based fire extinguishing agents have attracted attention due to their rapid film formation and excellent heat insulation properties. Single systems such as silica sol or alumina sol can form an inorganic gel layer on the surface of combustible materials, effectively isolating oxygen and cooling the area. However, existing single-sol systems still have significant shortcomings: First, flowability is difficult to control precisely, easily flowing on steep slopes or rough surfaces of forest combustibles (such as pine chips, leaf litter, etc.), failing to quickly form a uniform and dense covering layer; second, gel strength is insufficient, easily cracking and peeling at high temperatures, causing flames to reignite from the cracks; third, there is a lack of effective reignition prevention components, and the residual high temperatures after extinguishing the fire can easily trigger secondary combustion. The problem of rapid agent loss is particularly prominent on sloping forest surfaces, significantly reducing actual fire extinguishing efficiency. Furthermore, existing products rarely consider film formation speed, adhesion, and long-term reignition resistance.

[0004] Therefore, there is an urgent need to develop a forest fire extinguishing agent that forms a film quickly, adheres firmly, effectively inhibits reignition, and is environmentally friendly, in order to fill the existing technological gap and improve the success rate of forest fire suppression and the safety of the fire site. Summary of the Invention

[0005] The problem this invention aims to solve is to provide a forestry silica-alumina sol fire extinguishing agent, its preparation method, and its application, in order to address the issues of poor adhesion, poor resistance to reignition, complex composition, and easy stratification and precipitation in existing gel fire extinguishing agents.

[0006] The technical solution adopted to solve its technical problems is to provide a forest-use silica-alumina sol fire extinguishing agent, comprising liquid A and liquid B with a weight ratio of 2~30:1; Liquid A comprises the following raw materials in parts by weight: 15-35 parts silica sol, 2-20 parts aluminum sol, 0.01-0.4 parts sphingosine colloid, 1-5 parts flame retardant, 0.1-0.5 parts dispersant, 0.01-0.3 parts polysol and 50-70 parts water; Solution B comprises the following raw materials in parts by weight: 0.1-2 parts titanium gluconate and 5-15 parts water.

[0007] The beneficial effects of the above-mentioned technical solution of this invention are as follows: In the forestry silica-alumina sol fire extinguishing agent of this invention, the silica sol in component A provides a high-temperature resistant SiO2 glass phase, which constitutes the network structure matrix of the ceramic layer, mainly playing the role of heat absorption and oxygen isolation; the alumina sol provides an Al2O3 refractory phase, which increases the hardness and refractoriness of the ceramic layer, and works synergistically with the silica sol to form a dense inorganic skeleton, preventing the flame retardant layer from breaking; the sphingosine gel is a water-soluble polymer, which acts as a stabilizer to provide a viscoelastic skeleton for the gel, allowing the fire extinguishing agent to adhere firmly to the fuel surface and not easily flow; the flame retardant can be ceramicized and decomposed into a borate flux phase at high temperature, promoting the formation of a continuous and dense multi-element ceramic barrier layer of silicon, aluminum and titanium, mainly playing the role of heat insulation, smoke suppression and anti-reignition; the dispersant helps to reduce surface tension, plays the role of wetting, penetrating and dispersing raw materials, improves colloidal compatibility, makes spraying uniform and reduces particle agglomeration; the polysol, as a natural polymer, has the synergistic effects of antibacterial, slight thickening and film formation. Titanium gluconate in component B acts as a crosslinking agent, forming a stable crosslinking network with the sol and polysaccharides in solution A. This achieves mild and controllable crosslinking of polymer and inorganic sol networks, resulting in a gel with moderate strength and uniform, delicate texture.

[0008] Upon contact with a fire source, the forest-grade silica-alumina sol fire extinguishing agent of this invention first absorbs heat through rapid evaporation of a large amount of water in the system, quickly reducing the surface temperature of the combustible material. Simultaneously, a highly adhesive gel layer is formed under the action of a cross-linking network, tightly encapsulating the burning material and isolating oxygen from contact with air, preventing further spread of the fire. During the heating process, the silica sol and alumina sol are dehydrated to form a silica glass phase and an alumina refractory ceramic phase, respectively. Combined with the flux phase generated by the high-temperature decomposition of the flame retardant and the titanium dioxide reinforcing phase generated by the pyrolysis of titanium gluconate, the multiple components undergo a synergistic reaction to construct a continuous, dense, high-temperature resistant, and crack-resistant Si-Al-B-Ti-O multi-element ceramic barrier layer, effectively resisting heat radiation and preventing reignition. Furthermore, by capturing free radicals such as hydroxyl groups generated in the combustion chain reaction, the chemical chain reaction of combustion is interrupted, ultimately achieving an integrated fire extinguishing effect of cooling, oxygen isolation, flame suppression, and anti-reignition.

[0009] Preferably, the forest silica-alumina sol extinguishing agent comprises liquid A and liquid B in a weight ratio of 5 to 15:1; Liquid A comprises the following raw materials in parts by weight: 20-30 parts silica sol, 5-15 parts aluminum sol, 0.1-0.3 parts sphingosine colloid, 2-3 parts flame retardant, 0.2-0.4 parts dispersant, 0.1-0.2 parts polysol and 60-65 parts water; Solution B comprises the following raw materials in parts by weight: 0.5-1.5 parts titanium gluconate and 8-10 parts water.

[0010] More preferably, the forest silica-alumina sol extinguishing agent comprises liquid A and liquid B in a weight ratio of 10:1; Liquid A comprises the following raw materials in parts by weight: 25 parts silica sol, 10 parts aluminum sol, 0.2 parts sphingosine colloid, 2.5 parts flame retardant, 0.3 parts dispersant, 0.15 parts polysol and 61.85 parts water; Solution B comprises the following raw materials in parts by weight: 1 part titanium gluconate and 9 parts water.

[0011] More preferably, the silica sol has a pH of 8-9 and a solid content of 20-30%; the aluminum sol has a pH of 3-4 and a solid content of 20-25%.

[0012] More preferably, the flame retardant is polyborosiloxane, ammonium polyphosphate, magnesium hydroxide, or aluminum hydroxide.

[0013] More preferably, the dispersant is isooctyl glucoside; the polysolvent is ε-polylysine.

[0014] The present invention also provides a method for preparing the above-mentioned forestry silica-alumina sol fire extinguishing agent, comprising the following steps: (1) Under stirring conditions, silica sol, aluminum sol, flame retardant, polysol, dispersant and sphingosine gum are added to water in sequence to dissolve, and the solution is allowed to stand to defoam, thus obtaining solution A; (2) Take another water, and under stirring conditions, add titanium gluconate to dissolve it to obtain solution B; (3) Mix liquid A and liquid B to obtain the forest-grade silica-alumina sol fire extinguishing agent.

[0015] Preferably, the stirring speed in step (1) is 200~300 rpm; the standing defoaming time is 10~20 min.

[0016] More preferably, in step (1), silica sol, aluminum sol, flame retardant, polysol, dispersant and sphingosine gel are added to water in sequence to dissolve the following steps: add silica sol to water and stir for 4-6 minutes until the solution is transparent and uniform; add aluminum sol and stir for 8-12 minutes until the solution is semi-transparent; add flame retardant and stir for 8-12 minutes until the flame retardant is evenly dispersed; add polysol and stir for 4-6 minutes until the solution is transparent and uniform; add dispersant and stir for 4-6 minutes; and finally, evenly disperse sphingosine gel on the edge of the vortex formed by stirring and stir for 15-20 minutes.

[0017] Preferably, in step (2), the stirring speed is 150~100 rpm and the dissolution time is 5~10 min.

[0018] The present invention also provides the application of the above-mentioned forestry silica-alumina sol fire extinguishing agent in forest fire fighting.

[0019] The present invention has the following beneficial effects: (1) In the forest silica-alumina sol fire extinguishing agent of the present invention, the silica sol is positively charged and the aluminum sol is negatively charged. When the two are combined, the charge will be neutralized. When the flame is at high temperature or when sprayed, a dense and hard inorganic gel film is quickly formed. This film can isolate oxygen and resist high temperature, thereby improving the fire extinguishing efficiency. (2) In the forest silica-alumina sol fire extinguishing agent of the present invention, silica sol, alumina sol, polyboron siloxane and titanium gluconate work together to retard flame. When heated, a continuous, dense and high-temperature resistant Si-Al-B-Ti-O multi-element ceramic barrier layer is formed in situ, which realizes heat absorption and cooling, oxygen isolation, inhibition of molten dripping and enhanced anti-reignition performance. The overall flame retardant effect is far superior to that of traditional gel fire extinguishing agents. (3) The components of the A liquid in the forest silica-alumina sol fire extinguishing agent of the present invention have good chemical compatibility and mild pH. After being mixed with the B liquid, it forms a dense ceramic barrier layer at high temperature without collapsing. Overall, it has storage stability, chemical stability, use stability and strong adhesion. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of this invention, and not all of them.

[0021] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0022] The features and performance of the present invention will be further described in detail below with reference to the embodiments. The ε-polylysine used in the following embodiments has the CAS number 28211-04-3; the isooctyl glucoside has the CAS number 125590-73-0.

[0023] Example 1 A forestry silica-alumina sol fire extinguishing agent, comprising liquid A and liquid B in a weight ratio of 10:1; Solution A comprises the following raw materials in parts by weight: 25 parts silica sol, 10 parts aluminum sol, 0.2 parts sphingosine gum, 2.5 parts polyborosiloxane, 0.3 parts isooctyl glucoside, 0.15 parts ε-polylysine, and 61.85 parts deionized water; Solution B comprises the following raw materials in parts by weight: 1 part titanium gluconate and 9 parts deionized water; The silica sol has a pH of 8-9 and a solid content of 30%; the aluminum sol has a pH of 3-4 and a solid content of 20%.

[0024] This embodiment also discloses a method for preparing a forest-grade silica-alumina sol fire extinguishing agent, including the following steps: (1) Add deionized water from component A in a conical flask, turn on the stirrer and adjust the speed to 250 rpm, add silica sol and continue stirring for 5 min until the solution is clear and uniform, then add aluminum sol and stir for 10 min until the solution is translucent, then sprinkle polyborosiloxane into the liquid surface and stir for 10 min until it is completely dispersed and uniform without particles, then add ε-polylysine and stir for 5 min until the solution is clear and uniform, then add isooctyl glucoside and stir for 5 min until the surface tension of the solution decreases and a wetting sensation is produced, finally disperse sphingosine gel evenly on the edge of the vortex formed by stirring and stir for 15 min until it is completely dissolved, stop stirring, let stand for 15 min to defoam, and obtain solution A; (2) Take another deionized water from component B and place it in another conical flask. Turn on the stirrer and adjust the speed to 150 rpm. Add titanium gluconate to the deionized water and continue stirring for 10 minutes until completely dissolved. Stop stirring and seal and store in the dark to obtain a slightly yellow solution B. (3) Mix liquid A and liquid B and use immediately to obtain the forest-grade silica-alumina sol fire extinguishing agent.

[0025] Example 2 A forestry silica-alumina sol fire extinguishing agent, comprising liquid A and liquid B in a weight ratio of 12.4:1; Solution A comprises the following raw materials in parts by weight: 15 parts silica sol, 2 parts aluminum sol, 0.1 parts sphingosine gum, 1 part ammonium polyphosphate, 0.1 parts isooctyl glucoside, 0.1 parts ε-polylysine, and 50 parts deionized water; Solution B comprises the following raw materials in parts by weight: 0.5 parts titanium gluconate and 5 parts deionized water; The silica sol has a pH of 8-9 and a solid content of 30%; the aluminum sol has a pH of 3-4 and a solid content of 20%.

[0026] This embodiment also discloses a method for preparing a forest-grade silica-alumina sol fire extinguishing agent, including the following steps: (1) Add deionized water from component A in a conical flask, turn on the stirrer and adjust the speed to 200 rpm, add silica sol and continue stirring for 5 min until the solution is transparent and homogeneous, then add aluminum sol and stir for 10 min until the solution is translucent, then sprinkle ammonium polyphosphate into the liquid surface and stir for 10 min until it is completely dispersed and uniform without particles, then add ε-polylysine and stir for 5 min until the solution is transparent and homogeneous, then add isooctyl glucoside and stir for 5 min until the surface tension of the solution decreases and a wetting sensation is produced, finally disperse sphingosine gel evenly on the edge of the vortex formed by stirring and stir for 15 min until it is completely dissolved, stop stirring, let stand for 20 min to defoam, and obtain solution A; (2) Take another deionized water from component B and place it in another conical flask. Turn on the stirrer and adjust the speed to 100 rpm. Add titanium gluconate to the deionized water and continue stirring for 5 minutes until completely dissolved. Stop stirring and seal and store in the dark to obtain a slightly yellow solution B. (3) Mix liquid A and liquid B and use immediately to obtain the forest-grade silica-alumina sol fire extinguishing agent.

[0027] Example 3 A forestry silica-alumina sol fire extinguishing agent, comprising liquid A and liquid B in a weight ratio of 7.7:1; Solution A comprises the following raw materials in parts by weight: 35 parts silica sol, 20 parts aluminum sol, 0.4 parts sphingosine gum, 5 parts magnesium hydroxide, 0.5 parts isooctyl glucoside, 0.3 parts ε-polylysine, and 70 parts deionized water; Solution B comprises the following raw materials in parts by weight: 2 parts titanium gluconate and 15 parts deionized water; The silica sol has a pH of 8-9 and a solid content of 30%; the aluminum sol has a pH of 3-4 and a solid content of 20%.

[0028] This embodiment also discloses a method for preparing a forest-grade silica-alumina sol fire extinguishing agent, including the following steps: (1) Add deionized water from component A in a conical flask, turn on the stirrer and adjust the speed to 300 rpm, add silica sol and continue stirring for 5 min until the solution is transparent and uniform, then add aluminum sol and stir for 10 min until the solution is semi-transparent, then sprinkle magnesium hydroxide into the liquid surface and stir for 10 min until it is completely dispersed and uniform without particles, then add ε-polylysine and stir for 5 min until the solution is transparent and uniform, then add isooctyl glucoside and stir for 5 min until the surface tension of the solution decreases and a wetting sensation is produced, finally disperse sphingosine gel evenly on the edge of the vortex formed by stirring and stir for 15 min until it is completely dissolved, stop stirring, let stand for 15 min to defoam, and obtain solution A; (2) Take another deionized water from component B and place it in another conical flask. Turn on the stirrer and adjust the speed to 100 rpm. Add titanium gluconate to the deionized water and continue stirring for 10 minutes until completely dissolved. Stop stirring and seal and store in the dark to obtain a slightly yellow solution B. (3) Mix liquid A and liquid B and use immediately to obtain the forest-grade silica-alumina sol fire extinguishing agent.

[0029] Comparative Example 1 A forest-grade silica-alumina sol fire extinguishing agent differs from Example 1 in that it does not contain the sphingosine gum from Solution A, while the remaining raw materials and preparation method parameters are the same as in Example 1.

[0030] Comparative Example 2 A forest-grade silica-alumina sol fire extinguishing agent differs from Example 1 in that titanium gluconate in solution B is replaced with borax, while the remaining raw materials and preparation method parameters are the same as in Example 1.

[0031] Comparative Example 3 A forest-grade silica-alumina sol fire extinguishing agent differs from Example 1 in that it does not contain the aluminum sol from Solution A, while the remaining raw materials and preparation method parameters are the same as in Example 1.

[0032] Comparative Example 4 A forest-grade silica-alumina sol fire extinguishing agent differs from Example 1 in that it does not contain the polyborosiloxane from Solution A, while the remaining raw materials and preparation method parameters are the same as in Example 1.

[0033] Experimental Example 1. Fire extinguishing experiments were conducted on the forest silica-alumina sol fire extinguishing agents prepared in Example 1 and Comparative Examples 1-4.

[0034] (1) A comparative fire extinguishing effect experiment was conducted in a relatively enclosed fire extinguishing test space (2m×2m×2.5m). The ambient temperature was 10~30℃, and the ventilation and lighting conditions did not affect the free combustion of the fuel. In the experiment, the combustion pan was a square oil pan with a length and width of 31.64cm and a height of 16cm, and the bottom area of ​​the oil pan was 0.1m². 2 The bottom of the test chamber was lined with water, and the bottom of the oil pan was 22cm above the ground. 3L of soybean oil was used as fuel. First, 1.5-2.5L of water was added to the bottom of the oil pan, just enough to cover it. Then, the soybean oil was poured into the pan, ignited, and pre-ignited for 30 seconds. The test chamber door was then closed, and 100g of the forest silica-alumina sol extinguishing agent prepared in Example 1 and Comparative Examples 1-4 were sprayed into each chamber. Each group was tested three times, and the extinguishing time for each group was recorded and combined. (2) Ignite the oil pan with an igniter within 1 minute and observe its reignition. (3) Pine wood chips were used to simulate forest combustibles. The wood chips were fixed and tilted at 45°. The forest silica-alumina sol fire extinguishing agents prepared in Example 1 and Comparative Examples 1-4 were sprayed on the wood chips. The film-forming time and the time of stopping flow of the fire extinguishing agent on the wood chips were observed. The experiment was repeated 3 times. The results are shown in Table 1.

[0035] Table 1 Results of fire extinguishing experiments

[0036] As shown in Table 1, Example 1 exhibited the best fire extinguishing performance, which was attributed to the synergistic effect between the components. Sphingosine gel, a water-soluble polymer, can act as a stabilizer to provide the viscoelastic framework of the gel, allowing the extinguishing agent to adhere firmly to the fuel surface and prevent it from flowing, significantly improving the film-forming speed and flow control. Its absence would double the extinguishing time and significantly worsen the film-forming and flow-stopping times. Titanium gluconate, as a crosslinking agent, can form a stable crosslinking network with the sol and polysaccharides in Solution A, achieving mild and controllable crosslinking of polymers and inorganic sol networks, resulting in a moderate, uniform, and delicate gel. Its effect in promoting the sol-gel transition is better than that of traditional borax, and replacing it with borax significantly prolongs the extinguishing time. Aluminum sol is one of the core film-forming substances, which together with silica sol construct the inorganic gel framework. Its absence results in the longest extinguishing time and has the greatest impact on the extinguishing speed. Polyborosiloxane (flame retardant) provides the key function of preventing reignition, and can form a glassy protective layer at high temperatures. Its absence, although the initial fire extinguishing is still acceptable, will lead to reignition.

[0037] 2. Stability Test The stability of the forestry silica-alumina sol fire extinguishing agents prepared in Example 1 and Comparative Example 1 of this invention was measured using a centrifuge. The results showed that the forestry silica-alumina sol fire extinguishing agent prepared in Example 1 only showed a small amount of water precipitation and clumping when the centrifuge speed was 6000 r / min; while the forestry silica-alumina sol fire extinguishing agent prepared in Comparative Example 1 showed a small amount of water precipitation and clumping when the centrifuge speed was 2000 r / min. This indicates that the forestry silica-alumina sol fire extinguishing agent of this invention has good stability and is not prone to stratification and sedimentation.

[0038] The present invention has been described according to the above embodiments. It should be understood that the above embodiments do not limit the present invention in any way. All technical solutions obtained by equivalent substitution or equivalent transformation fall within the scope of the present invention.

Claims

1. A forestry silica-alumina sol fire extinguishing agent, characterized in that, This includes solution A and solution B with a weight ratio of 2 to 30:1; Liquid A comprises the following raw materials in parts by weight: 15-35 parts silica sol, 2-20 parts aluminum sol, 0.01-0.4 parts sphingosine colloid, 1-5 parts flame retardant, 0.1-0.5 parts dispersant, 0.01-0.3 parts polysol and 50-70 parts water; The B solution comprises the following raw materials in parts by weight: 0.1-2 parts titanium gluconate and 5-15 parts water.

2. The forestry silica-alumina sol fire extinguishing agent as described in claim 1, characterized in that, This includes liquid A and liquid B with a weight ratio of 5 to 15:1; Liquid A comprises the following raw materials in parts by weight: 20-30 parts silica sol, 5-15 parts aluminum sol, 0.1-0.3 parts sphingosine colloid, 2-3 parts flame retardant, 0.2-0.4 parts dispersant, 0.1-0.2 parts polysol and 60-65 parts water; The B solution comprises the following raw materials in parts by weight: 0.5-1.5 parts titanium gluconate and 8-10 parts water.

3. The forestry silica-alumina sol fire extinguishing agent as described in claim 2, characterized in that, This includes solution A and solution B in a weight ratio of 10:1; Liquid A comprises the following raw materials in parts by weight: 25 parts silica sol, 10 parts aluminum sol, 0.2 parts sphingosine colloid, 2.5 parts flame retardant, 0.3 parts dispersant, 0.15 parts polysol and 61.85 parts water; The B solution comprises the following raw materials in parts by weight: 1 part titanium gluconate and 9 parts water.

4. The forestry silica-alumina sol fire extinguishing agent according to any one of claims 1 to 3, characterized in that, The silica sol has a pH of 8-9 and a solid content of 20-30%; the aluminum sol has a pH of 3-4 and a solid content of 20-25%.

5. The forestry silica-alumina sol fire extinguishing agent according to any one of claims 1 to 3, characterized in that, The flame retardant is polyborosiloxane, ammonium polyphosphate, magnesium hydroxide, or aluminum hydroxide.

6. The forestry silica-alumina sol fire extinguishing agent according to any one of claims 1 to 3, characterized in that, The dispersant is isooctyl glucoside; the polysolvent is ε-polylysine.

7. The method for preparing the forestry silica-alumina sol fire extinguishing agent according to any one of claims 1 to 6, characterized in that, Includes the following steps: (1) Under stirring conditions, silica sol, aluminum sol, flame retardant, polysol, dispersant and sphingosine gum are added to water in sequence to dissolve, and the solution is allowed to stand to defoam, thus obtaining solution A; (2) Take another water, and under stirring conditions, add titanium gluconate to dissolve it to obtain solution B; (3) Mix liquid A and liquid B to obtain the forest-grade silica-alumina sol fire extinguishing agent.

8. The preparation method of the forestry silica-alumina sol fire extinguishing agent as described in claim 7, characterized in that, In step (1), the stirring speed is 200~300 rpm; the settling and defoaming time is 10~20 min.

9. The preparation method of the forestry silica-alumina sol fire extinguishing agent as described in claim 7, characterized in that, In step (2), the stirring speed is 150~100 rpm; the dissolution time is 5~10 min.

10. The application of the forest-grade silica-alumina sol extinguishing agent according to any one of claims 1 to 6 in forest fire fighting.

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