Hydromagnesite-based fire extinguishing powder, preparation method and application thereof

Abstract

The application discloses a kind of water magnesite-based fire extinguishing powder and its preparation method and application.The fire extinguishing powder of the application includes the fire extinguishing powder includes modified water magnesite and dry powder additive;The modified water magnesite powder is the water magnesite powder with modifier on surface;The modifier is selected from MHCO3, and M is monovalent metal ion.The modifier is loaded to the surface of water magnesite powder in the application, and water magnesite powder is given chemical inhibition effect, and the fire extinguishing efficiency thereof is further improved on the basis of physical inhibition;And by adding other inert ingredients, the hydrophobicity and oleophobicity, flowability and dispersion effect of water magnesite powder are improved, and the agglomeration phenomenon is reduced, so that the comprehensive performance reaches the design standard of dry powder fire extinguishing agent specified by the state.

Description

Technical Field

[0001] This invention relates to the technical field of fire extinguishing agents, specifically to a fire extinguishing powder based on hydromagnesite, its preparation method, and its application. Background Technology

[0002] Dry powder extinguishing agents are one of the most common halon alternatives, offering advantages such as short extinguishing time, low production cost, low corrosivity, convenient storage, easy transportation, wide extinguishing range, and no environmental pollution. These advantages have attracted increasing attention from scientists and scholars both domestically and internationally, indicating promising application prospects. Dry powder extinguishing agents can be used as a clean and efficient halon alternative.

[0003] The particle size (D90) of ordinary dry powder extinguishing agents is generally greater than 40 μm. In recent years, with further research, researchers have found that the extinguishing efficiency of dry powder extinguishing agents increases exponentially with the reduction of particle size. Researchers have added grinding aids, dispersants, moisture-proofing agents, antistatic agents, and rheology modifiers to existing ordinary dry powders, and through mechanical grinding and air jet milling, have reduced the particle size to below 20 μm to produce ultrafine dry powder extinguishing agents. However, ultrafine dry powder extinguishing agents have many drawbacks. On the one hand, the particles are prone to agglomeration, which not only leads to insufficient flowability of the extinguishing agent but also reduces its extinguishing efficiency. Furthermore, the particles have poor oleophobic properties and cannot effectively extinguish oil fires. On the other hand, ultrafine dry powder particles mean a significant increase in production costs, and the preparation process is complex, thus limiting its commercial application. Currently, most ultrafine dry powder extinguishing agents remain in the laboratory research stage, and many problems need to be solved before large-scale commercial application.

[0004] Given the drawbacks of ordinary dry powder and ultrafine dry powder, there is an urgent need for a dry powder fire extinguishing agent with a particle size (D90) between 20-40μm, low production cost, simple preparation process, and high fire extinguishing efficiency.

[0005] Magnesite (Mg5(CO3)4(OH)2·4H2O, abbreviated as HM) is a naturally occurring basic carbonate mineral that has been discovered in many parts of the world. It boasts advantages such as large proven reserves, high purity, low price, and easy mining. Finely ground magnesite, used as the main extinguishing agent, replaces traditional BC and ABC dry powders, providing more alternatives to halon extinguishing agents. When heated, this substance decomposes, releasing water and carbon dioxide, which lowers the temperature at the fire scene and dilutes the oxygen concentration. The final pyrolysis product, magnesium oxide, forms a dense insulating layer, providing good suffocation and preventing reignition. Its extinguishing mechanism mainly involves cooling, dilution, and suffocation. The pyrolysis of magnesite does not produce corrosive acidic substances, causing no damage to equipment and is environmentally friendly, giving it significant application potential and development value.

[0006] However, natural HM has poor dispersibility, with inconsistent particle size and poor regularity; after being pulverized and refined, natural HM tends to agglomerate; HM dry powder mainly extinguishes flames through physical suppression, resulting in limited fire extinguishing efficiency, thus posing a certain disadvantage compared to ABC and BC type dry powders. Turning the disadvantages of HM dry powder into advantages and preparing high-performance HM dry powder is crucial. Summary of the Invention

[0007] The purpose of this invention is to overcome the deficiencies in the prior art and provide a fire extinguishing powder based on hydromagnesite, its preparation method, and its application. This invention uses a Raymond mill to pulverize and refine hydromagnesite into hydromagnesite powder; and loads a modifier onto the surface of the hydromagnesite powder, giving it a chemical inhibition effect that further enhances its fire extinguishing efficiency on the basis of physical inhibition; and by adding dry powder additives such as silicone oil, hydrophobic nano-SiO2, magnesium stearate, and talc, the hydrophobic and oleophobic properties, flowability, and dispersion effect of the hydromagnesite powder are improved, reducing agglomeration and ensuring that its overall performance meets the national design standards for dry powder fire extinguishing agents.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] One of the objectives of this invention is to provide a fire extinguishing powder based on hydromagnesite, the fire extinguishing powder comprising modified hydromagnesite and dry powder additives;

[0010] The modified hydromagnesite powder is hydromagnesite powder with a surface modifier; the modifier is selected from MHCO3, where M is a monovalent metal ion.

[0011] In the fire extinguishing powder based on hydromagnesite described in this invention, preferably,

[0012] A second objective of this invention is to provide a method for preparing fire extinguishing powder based on hydromagnesite as described in any one of the objectives of this invention, comprising the following steps:

[0013] Modified magnesite powder was mixed with dry powder additives, dried, and then fire extinguishing powder based on magnesite was obtained.

[0014] The modified hydromagnesite powder is selected from at least one of the following: modified hydromagnesite powder prepared by wet impregnation of hydromagnesite powder in a modifier solution, and modified hydromagnesite powder prepared by dry coating of the modifier onto the surface of hydromagnesite powder.

[0015] In the preparation method of fire extinguishing powder based on hydromagnesite according to the present invention, preferably,

[0016] The dry powder additive is silicone oil, hydrophobic nano-SiO2, magnesium stearate, and talc; preferably,

[0017] The hydrophobic nano-SiO2 has a D90 of 13-17 nm and a specific surface area of ​​250-350 m² / g; and / or,

[0018] The magnesium stearate has a D90 of 5-10 μm; and / or,

[0019] The talc powder has a D90 of 2.5-4 μm; and / or,

[0020] The modified magnesite powder is mixed with silicone oil, hydrophobic nano-SiO2, magnesium stearate, and talc powder using a high-speed airflow mixer. Preferably, the speed of the high-speed airflow mixer is controlled at 6000-8000 r / min and maintained for 5-10 min; and / or,

[0021] The drying method is freeze drying.

[0022] In the preparation method of fire extinguishing powder based on hydromagnesite according to the present invention, preferably,

[0023] The specific steps for preparing modified magnesite powder by wet impregnation of magnesite powder in a modifier solution include:

[0024] (1-1) Add hydromagnesite powder to the modified aqueous solution and mix well to obtain a suspension;

[0025] (1-2) The suspension is separated into solid and liquid, and the solid is dried to obtain modified hydromagnesite powder.

[0026] In the preparation method of fire extinguishing powder based on hydromagnesite according to the present invention, preferably,

[0027] The mass ratio of modifier to magnesite powder in the modifier aqueous solution is 10-20:100; and / or,

[0028] The mass ratio of water in the aqueous solution of hydromagnesite powder and modifier is 0.8-1:5; and / or,

[0029] The temperature for thorough mixing is 30-50℃; and / or,

[0030] Preferably, the magnesite powder is added to the modifier aqueous solution and then dispersed in a hydraulic lifting high-speed disperser to obtain a dispersion; more preferably, the hydraulic high-speed disperser has a working power of 7.5-9 kW, a total working time of 20-40 min, a single working time of 8-12 s, and a working interval of 10-20 s; and / or,

[0031] The dispersion was uniformly stirred using a cantilever stirrer to obtain a suspension; the rotation speed of the cantilever stirrer was 1200-1500 rpm, and the stirring time was 6-8 hours.

[0032] The pH value of the modifier aqueous solution is 8-10; preferably, the preparation method of the modifier aqueous solution includes the following steps:

[0033] The modifier is pre-dissolved in deionized water to obtain a hydrolysis solution. After complete dissolution, the pH value is adjusted to 8-10. More preferably, the complete dissolution is carried out by stirring under heating conditions. The heating temperature is 50-60℃ and the stirring time is 0.5-1h.

[0034] Potassium bicarbonate and sodium bicarbonate are weak bases with a pH between 8 and 9. For dry modification, considering practical application scenarios, not adjusting the pH of the sample will not have a substantial impact (the pH of hydromagnesite is also between 8 and 9). When modifying by wet impregnation, adjusting the pH of the solution is to improve experimental accuracy. Making the pH values ​​of the two similar can reduce experimental errors and increase the loading rate of the suspension.

[0035] In the preparation method of fire extinguishing powder based on hydromagnesite according to the present invention, preferably,

[0036] The solid-liquid separation of the suspension is performed by centrifugation, preferably in a refrigerated centrifuge; more preferably, the refrigerated centrifuge is operated at a speed of 3000-5000 r / min, at a temperature of (-5)-(-10)℃, and for a time of 8-10 min; and / or,

[0037] The drying method is freeze drying, preferably freeze drying in a vacuum freeze dryer, and more preferably, the freeze drying temperature is (-10)-(-20)℃, and the temperature is maintained for 4-6 hours to obtain modified hydromagnesite powder.

[0038] In the preparation method of fire extinguishing powder based on hydromagnesite according to the present invention, preferably,

[0039] The specific steps for preparing modified magnesite powder by dry coating a modifier onto the surface of magnesite powder include:

[0040] Magnesia silicoes powder was placed in a coating and modification machine hopper, then a modifier was added for coating and modification, and dried to obtain modified magnesia silicoes powder.

[0041] Preferably,

[0042] The mass ratio of modifier to hydrated magnesite powder is 10-20:100; and / or,

[0043] The equivalent diameter of the modifier is 0.5-1 mm; and / or,

[0044] The coating modification machine has a working power of 4-6 kW and a coating time controlled at 30-50 min; and / or,

[0045] The drying method is freeze drying, preferably freeze drying in a vacuum freeze dryer, and more preferably, the freeze drying temperature is (-10)-(-20)℃, and the temperature is maintained for 4-6 hours to obtain modified hydromagnesite powder.

[0046] In the preparation method of fire extinguishing powder based on hydromagnesite according to the present invention, preferably,

[0047] Hydromagnesite powder is selected from hydromagnesite powder with a particle size D90 of less than 45μm;

[0048] Preferably, the preparation method of hydromagnesia powder includes using natural hydromagnesia ore as raw material, refining the powder, and then vacuum freeze-drying and screening the hydromagnesia powder with a particle size D90 of less than 45 μm using an air classifier.

[0049] More preferably,

[0050] The equivalent diameter of the natural hydromagnesite is 200 mm, and the purity is ≥98%; and / or,

[0051] Natural hydromagnesite ore was pulverized and refined using a Raymond mill, with the rotation speed controlled at 320-400 r / min and the time controlled at 60-120 min.

[0052] In the method for preparing fire extinguishing powder based on hydromagnesite according to the present invention, more preferably, it includes the following steps:

[0053] (1) Select hydromagnesia as raw material. The ore is crushed and refined into hydromagnesia powder by Raymond mill. The speed of Raymond mill is controlled at 320-400 r / min and the time is controlled at 60-120 min. After vacuum freeze drying and sieving, hydromagnesia powder with uniform particle size distribution is obtained.

[0054] (2) Pre-hydrolysis of surface modifier: Dissolve the modifier in deionized water and stir magnetically for 0.5 h to ensure complete dissolution. Maintain the temperature at 50-60℃ to accelerate dissolution. After complete dissolution, adjust the pH to 8-10 and maintain the temperature.

[0055] (3) Surface modification by impregnation method: After step (2) is completed, the temperature is reduced to 30-40℃ and maintained throughout the process; the hydromagnesia powder prepared in step (1) is added to the pre-hydrolyzed solution prepared in step (2), and then placed in a hydraulic lifting high-speed disperser to obtain a dispersion. The hydraulic high-speed disperser has a working power of 7.5-9kw, a total working time of 20-40min, a single working time of 8-12s, and a working interval of 10-20s; the dispersion is uniformly stirred using a cantilever stirrer to obtain a suspension; the rotation speed of the cantilever stirrer is 1200-1500rpm, and the stirring time is 6-8h;

[0056] (4) Place the suspension in (3) into a refrigerated centrifuge and centrifuge. Control the speed of the refrigerated centrifuge at 3000-5000 r / min, control the temperature at (-5)-(-10)℃, and control the time at 8-10 min. After centrifugation, place it into a vacuum freeze dryer for freeze drying. Keep the temperature at (-10)-(-20)℃ for 4-6 h to obtain the preliminary modified powder.

[0057] (5) Preparation of modified hydromagnesia powder: The preliminary modified powder obtained in step (4) is added to silicone oil, hydrophobic nano SiO2, magnesium stearate and talc powder for high-speed mixing. The high-speed airflow mixer is controlled at 6000-8000 r / min, maintained for 5-10 min and then freeze-dried twice to obtain the finished modified hydromagnesia powder.

[0058] (6) Dry modification of powder: The hydromagnesia powder obtained in step (1) is placed in the hopper of the coating modification machine, and then surface modifier is added in proportion for coating modification. The working power of the coating modification machine is 4-6kw, and the coating modification time is controlled at 30-50min.

[0059] (7) Place the powder obtained in (6) into a vacuum freeze dryer for freeze drying at a temperature of (-10)-(-20)℃ for 4-6 hours to obtain a preliminary modified powder;

[0060] (8) Preparation of modified hydromagnesia dry powder: The preliminary modified powder obtained in step (7) is added to silicone oil, hydrophobic nano SiO2, magnesium stearate and talc powder for high-speed mixing at a speed of 6000-8000 r / min and kept for 5-10 min to reduce to the original particle size. After a second freeze-drying, the finished modified hydromagnesia dry powder is obtained.

[0061] In step (1), hydromagnesite is a natural mineral material mined in open-pit mines. After being crushed and refined, it is used as a raw material for fire extinguishing powder.

[0062] In step (1), the instrument used for pulverizing and refining is a Raymond mill, the instrument used for sieving is an air classifier, and the instrument used for drying is a vacuum freeze dryer; in step (2), the instrument used for stirring is an electrically heated magnetic stirrer; in step (3), the instrument used for dispersing is a hydraulic high-speed disperser; in step (4), the instrument used for centrifugation is a refrigerated centrifuge, and the instrument used for drying is a vacuum freeze dryer; in step (5), the instrument used for mixing is a high-speed airflow mixer, and the instrument used for secondary freeze drying is a vacuum freeze dryer; in step (6), the instrument used for dry coating modification is a coating modification machine; in step (7), the instrument used for drying is a vacuum freeze dryer; in step (8), the instrument used for mixing is a high-speed airflow mixer, and the instrument used for secondary freeze drying is a vacuum freeze dryer.

[0063] In the method for preparing fire extinguishing powder based on hydromagnesite according to the present invention, more preferably, it includes the following steps:

[0064] (1) Select hydromagnesia as raw material. The ore is crushed and refined into hydromagnesia powder by Raymond mill. The speed of Raymond mill is controlled at 320-400 r / min and the time is controlled at 60-120 min. After vacuum freeze drying and sieving, hydromagnesia powder with uniform particle size distribution is obtained.

[0065] (2) Pre-hydrolysis of surface modifier: Dissolve the modifier in deionized water and stir magnetically for 0.5 h to ensure complete dissolution. Maintain the temperature at 50-60℃ to accelerate dissolution. After complete dissolution, adjust the pH to 8-10 and maintain the temperature.

[0066] (3) Surface modification by impregnation method: After step (2) is completed, the temperature is reduced to 30-40℃ and maintained throughout the process; the hydromagnesia powder prepared in step (1) is added to the pre-hydrolyzed solution prepared in step (2), and then placed in a hydraulic lifting high-speed disperser to obtain a dispersion. The hydraulic high-speed disperser has a working power of 7.5-9kw, a total working time of 20-40min, a single working time of 8-12s, and a working interval of 10-20s; the dispersion is uniformly stirred using a cantilever stirrer to obtain a suspension; the rotation speed of the cantilever stirrer is 1200-1500rpm, and the stirring time is 6-8h;

[0067] (4) Place the suspension in (3) into a refrigerated centrifuge and centrifuge. Control the speed of the refrigerated centrifuge at 3000-5000 r / min, control the temperature at (-5)-(-10)℃, and control the time at 8-10 min. After centrifugation, place it into a vacuum freeze dryer for freeze drying. Keep the temperature at (-10)-(-20)℃ for 4-6 h to obtain the preliminary modified powder.

[0068] (5) Preparation of modified hydromagnesia powder: The preliminary modified powder obtained in step (4) is added to silicone oil, hydrophobic nano SiO2, magnesium stearate and talc powder for high-speed mixing. The high-speed airflow mixer is controlled at 6000-8000 r / min, maintained for 5-10 min and then freeze-dried twice to obtain the finished modified hydromagnesia powder.

[0069] (6) Dry modification of powder: The hydromagnesia powder obtained in step (1) is placed in the hopper of the coating modification machine, and then surface modifier is added in proportion for coating modification. The working power of the coating modification machine is 4-6kw, and the coating modification time is controlled at 30-50min.

[0070] (7) Place the powder obtained in (6) into a vacuum freeze dryer for freeze drying at a temperature of (-10)-(-20)℃ for 4-6 hours to obtain a preliminary modified powder;

[0071] (8) Preparation of modified hydromagnesia dry powder: The preliminary modified powder obtained in step (7) is added to silicone oil, hydrophobic nano SiO2, magnesium stearate and talc powder for high-speed mixing at a speed of 6000-8000 r / min and kept for 5-10 min to reduce to the original particle size. After a second freeze-drying, the finished modified hydromagnesia dry powder is obtained.

[0072] In step (1), hydromagnesite is a natural mineral material mined in open-pit mines. After being crushed and refined, it is used as a raw material for fire extinguishing powder.

[0073] In step (1), the instrument used for pulverizing and refining is a Raymond mill, the instrument used for sieving is an air classifier, and the instrument used for drying is a vacuum freeze dryer; in step (2), the instrument used for stirring is an electrically heated magnetic stirrer; in step (3), the instrument used for dispersing is a hydraulic high-speed disperser; in step (4), the instrument used for centrifugation is a refrigerated centrifuge, and the instrument used for drying is a vacuum freeze dryer; in step (5), the instrument used for mixing is a high-speed airflow mixer, and the instrument used for secondary freeze drying is a vacuum freeze dryer; in step (6), the instrument used for dry coating modification is a coating modification machine; in step (7), the instrument used for drying is a vacuum freeze dryer; in step (8), the instrument used for mixing is a high-speed airflow mixer, and the instrument used for secondary freeze drying is a vacuum freeze dryer.

[0074] A third objective of this invention is to provide an application of the fire extinguishing powder based on hydromagnesite as described in any one of the objectives of this invention in fire extinguishing.

[0075] The inventors of this invention discovered that the pH value of magnesite powder is around 8.5, and fire extinguishing experiments proved that HM dry powder has no chemical inhibitory effect (it lacks or has very weak ability to capture combustion free radicals). The inventors further discovered that when sodium bicarbonate and potassium bicarbonate, with pH values ​​similar to magnesite powder, are used as modifiers to modify magnesite powder, they not only possess the physical inhibitory effect of magnesite powder but also the chemical inhibitory effect of sodium bicarbonate and potassium bicarbonate, respectively. Moreover, the two have a synergistic effect, which can further improve the fire extinguishing effect of magnesite powder.

[0076] Compared with the prior art, the present invention has at least the following advantages:

[0077] The method of this invention is used to prepare a green, environmentally friendly, economical, simple to prepare, and highly effective fire extinguishing modified HM ordinary dry powder.

[0078] The hydromagnesite itself has hydrophilic and oleophobic properties. Adding silicone oil and nano-hydrophobic silica can give the hydromagnesite powder a hydrophobic effect, reduce its hygroscopicity, prevent dry powder from clumping, and thus improve its storage time. Adding magnesium stearate and talc can improve the fluidity and dispersion effect of the hydromagnesite powder and reduce its agglomeration. Attached Figure Description

[0079] Figure 1 This is a flowchart illustrating the preparation method of the modified hydrated magnesium oxide dry powder using a surface modifier according to the present invention.

[0080] Figure 2 The 1m used in the fire extinguishing experiment of this invention 3 Small-scale fire extinguishing experimental platform;

[0081] Figure 3 These are comparative SEM images of HM ordinary dry powder modified by the impregnation and coating method in Example 1 of this invention, and of HM ordinary dry powder as a blank control and commercial ABC ordinary dry powder. Figure 3 (a) is the HM ordinary dry powder modified by impregnation and coating method prepared in Example 1. Figure 3 (b) is the blank control HM ordinary dry powder. Figure 3 (c) is commercial ABC general dry powder.

[0082] Figure 4 The XRD data are for the modified hydromagnesite powder obtained by the impregnation and coating method in Example 1 of this invention.

[0083] Figure 5 The data provided are comparative adsorption-desorption curves and specific surface area (BET) data of HM ordinary dry powder modified by impregnation and coating method in Example 1 of this invention, blank control HM ordinary dry powder and commercial ABC ordinary dry powder.

[0084] Figure 6 This is a comparison chart of TG-DSC data between HM ordinary dry powder modified by impregnation and coating method in Example 1 of the present invention, blank control HM ordinary dry powder, and commercial ABC ordinary dry powder. Figure 6 (a) is the thermogravimetric (TG) curve. Figure 6 (b) shows the thermal decomposition rate (DTG) curve. Figure 6 (c) shows the differential scanning calorimetry (DSC) curve.

[0085] Figure 7 The images shown are screenshots from a video comparing the fire extinguishing effects of the impregnation-coating modified HM ordinary dry powder (as described in Example 1 of this invention), the blank control HM ordinary dry powder, and commercial ABC ordinary dry powder. Figure 7 (a) Screenshot from a video showing HM ordinary dry powder fire extinguishing agent modified by impregnation and coating method. Figure 7 (b) is a screenshot from a video of HM ordinary dry powder fire extinguishing system, which is the blank control. Figure 7(c) is a screenshot from a commercial ABC ordinary dry powder fire extinguishing video.

[0086] Figure 8 This is a comparison of the temperature reduction values ​​of HM ordinary dry powder modified by the impregnation and coating method in Example 1 of the present invention, and commercial ABC ordinary dry powder after 10 seconds of release. Figure 8 (a) shows the temperature change curve of HM ordinary dry powder modified by impregnation and coating method. Figure 8 (b) shows the temperature change curve of the blank control HM ordinary dry powder. Figure 8 (c) shows the temperature change curve of commercial ABC ordinary dry powder.

[0087] Figure 9 This invention provides a comparison of the smoke suppression effect (CO concentration) of HM ordinary dry powder modified by impregnation and coating method in Example 1 of the present invention, and a blank control HM ordinary dry powder and commercial ABC ordinary dry powder.

[0088] Explanation of reference numerals in the attached figures:

[0089] 1-Pressure tank, 2-High-speed camera, 3-Data acquisition device, 4-Flue gas analyzer, 5-Pressure gauge, 6-Nozzle, 7-Nitrogen cylinder, 8-K-type thermocouple, 9-Oil pan. Detailed Implementation

[0090] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0091] Example 1

[0092] A method for preparing fire extinguishing powder based on hydromagnesite includes the following steps:

[0093] (1) Preparation of ordinary magnesia ore powder: Natural magnesia ore was selected as raw material. The magnesia ore was placed in the Raymond mill bin and then crushed and refined by Raymond mill at a speed of 320 r / min for 60 min. After the process, it was vacuum freeze-dried and screened by air classifier to obtain ordinary magnesia ore powder with a particle size (D90) of less than 45 μm.

[0094] (2) Pre-dissolving the surface modifier: Dissolve potassium bicarbonate in deionized water to obtain a hydrolysis solution; stir magnetically for 0.5 h to fully dissolve it, and keep the temperature at 60℃ to accelerate the dissolution; adjust the pH value to 8.5 with deionized water.

[0095] (3) Impregnation and coating modification of ordinary magnesite powder (D90 < 45 μm): After step (2) is completed, the temperature is reduced to 50℃ and maintained throughout the process; the ordinary magnesite powder prepared in step (1) is added to the pre-hydrolysis solution in step (2), wherein the ordinary magnesite powder in step (1) and the surface modifier solution in step (2) are prepared according to the mass ratio of magnesite powder to dispersant deionized water of 1:5, and the mass ratio of potassium bicarbonate to magnesite powder of 20:100; the above mixture is placed in a hydraulic lifting high-speed disperser to disperse and obtain a dispersion liquid. The hydraulic high-speed disperser has a working power of 7.5kw, a total working time of 20min, a single working time of 8s, and a working interval of 10s; the dispersion liquid is uniformly stirred using a cantilever stirrer to obtain a suspension liquid; the rotation speed of the cantilever stirrer is 1200rpm, and the stirring time is 6h;

[0096] (4) The suspension in (3) was placed in a refrigerated centrifuge for centrifugation. The speed of the refrigerated centrifuge was controlled at 3500 r / min, the temperature was controlled at -5℃, and the time was controlled at 10 min. After centrifugation, it was placed in a vacuum freeze dryer for freeze drying. The temperature was kept at -15℃ for 5 h to obtain the preliminary modified powder.

[0097] (5) Preparation of ordinary HM dry powder modified by impregnation and coating method: The preliminary modified powder obtained in step (4) is added to silicone oil, hydrophobic nano SiO2, magnesium stearate and talc powder for high-speed mixing. The mass ratio of modified magnesite powder, silicone oil, hydrophobic nano silica, magnesium stearate and talc powder is 100:1:3.5:3:2.5. The high-speed airflow mixer is controlled at a speed of 6000 r / min and kept for 5 min to reduce to the original particle size (D90 < 45 μm). After a second freeze-drying (vacuum freeze dryer temperature -10℃ for 12 hours), the finished ordinary modified HM dry powder is obtained.

[0098] Example 2

[0099] A method for preparing fire extinguishing powder based on hydromagnesite includes the following steps:

[0100] (1) Preparation of ordinary hydromagnesia ore powder: Natural hydromagnesia ore was selected as raw material. The hydromagnesia ore was placed in the Raymond mill bin and then crushed and refined by Raymond mill at a speed of 400 r / min for 120 min. After the process, it was vacuum freeze-dried and screened by air classifier to obtain ordinary hydromagnesia ore powder with a particle size (D90) of less than 30 μm.

[0101] (2) Pre-dissolving the surface modifier: Dissolve potassium bicarbonate in deionized water to obtain a hydrolysis solution; stir magnetically for 1 hour to fully dissolve it, and keep the temperature at 60℃ to accelerate the dissolution; adjust the pH value to 8.5 with deionized water.

[0102] (3) Impregnation and coating modification of ordinary magnesite powder (D90 < 30 μm): After step (2) is completed, the temperature is reduced to 50℃ and maintained throughout the process; the ordinary magnesite powder prepared in step (1) is added to the pre-hydrolysis solution in step (2), wherein the ordinary magnesite powder in step (1) and the surface modifier solution in step (2) are prepared according to the mass ratio of magnesite powder to dispersant deionized water of 0.8:5 and the mass ratio of potassium bicarbonate to magnesite powder of 15:100. The above mixture is placed in a hydraulic lifting high-speed disperser to obtain a dispersion. The hydraulic high-speed disperser has a working power of 8kw, a total working time of 40min, a single working time of 12s, and a working interval of 20s; the dispersion is uniformly stirred using a cantilever stirrer to obtain a suspension; the rotation speed of the cantilever stirrer is 1500rpm and the stirring time is 8h;

[0103] (4) The suspension in (3) was placed in a refrigerated centrifuge for centrifugation. The speed of the refrigerated centrifuge was controlled at 4500 r / min, the temperature was controlled at -10℃, and the time was controlled at 10 min. After centrifugation, it was placed in a vacuum freeze dryer for freeze drying. The temperature was kept at -15℃ for 5 h to obtain ordinary modified particles.

[0104] (5) Preparation of ordinary HM dry powder modified by impregnation and coating method: The ordinary modified particles obtained in step (4) are added to silicone oil, hydrophobic nano-SiO2, magnesium stearate and talc powder and mixed at high speed. The mass ratio of ordinary modified particles, silicone oil, hydrophobic nano-silica, magnesium stearate and talc powder is 100:1:5:3:1. The rotation speed is 6000r / min and maintained for 10min to reduce to the original particle size (D90<30μm). After a second freeze-drying (vacuum freeze dryer temperature -15℃ for 12 hours), the finished ordinary modified HM dry powder is obtained.

[0105] Example 3

[0106] A method for preparing fire extinguishing powder based on hydromagnesite includes the following steps:

[0107] (1) Preparation of ordinary magnesia ore powder: Natural magnesia ore was selected as raw material. The magnesia ore was placed in the Raymond mill bin and then crushed and refined by Raymond mill at a speed of 320 r / min for 60 min. After the process, it was vacuum freeze-dried and screened by air classifier to obtain ordinary magnesia ore powder with a particle size (D90) of less than 45 μm.

[0108] (2) Dry modification of ordinary hydromagnesite powder (D90 < 45 μm): The ordinary hydromagnesite powder obtained in step (1) is placed in the hopper of the coating modification machine, and then potassium bicarbonate (equivalent diameter of 0.5-1 mm) is added in proportion for coating modification. The ratio of potassium bicarbonate to ordinary hydromagnesite powder is 10:100. The working power of the coating modification machine is 4 kW, and the coating modification time is controlled at 30 min.

[0109] (3) The coated modified powder obtained in (2) was placed in a vacuum freeze dryer and freeze-dried at -15℃ for 5 hours to obtain the preliminary modified powder;

[0110] (4) Preparation of HM dry powder by coating and modification machine: The preliminary modified powder obtained in step (3) is added to silicone oil, hydrophobic nano-SiO2, magnesium stearate and talc powder for high-speed mixing. The mass ratio of preliminary modified powder, silicone oil, hydrophobic nano-silica, magnesium stearate and talc powder is 100:0.5:4.5:1.5:3.5. The high-speed airflow mixer rotates at 8000 r / min and is kept for 5 min to reduce to the normal particle size (D90<45μm). After a second freeze-drying (held at -15℃ in a vacuum freeze dryer for 12 hours), the finished ordinary modified HM dry powder is obtained.

[0111] This invention provides a green, environmentally friendly, economical, simple, and highly effective modified HM ordinary dry powder for fire extinguishing. The raw material is magnesite, a natural mineral material. The magnesite is pulverized into fine powder, which is then modified and additives are introduced to obtain the modified HM ordinary dry powder. Magnesite is widely used in flame-retardant materials. This invention expands its application areas and explores its fire extinguishing potential, enabling specific applications in fire suppression. Furthermore, this invention provides a novel, highly effective fire extinguishing agent formulation that meets current application needs.

[0112] This invention involves pulverizing and refining hydromagnesite and modifying it. Modifiers such as potassium bicarbonate are selected, and wet modification (impregnation coating method) and dry modification (coating modification machine modification) are used to impart chemical inhibition effects to the hydromagnesite, further improving its fire extinguishing efficiency on the basis of physical inhibition. The addition of inert components such as silicone oil, hydrophobic nano-silica, magnesium stearate, and talc further enhances the overall performance of ordinary modified HM dry powder. The specific process flow is as follows... Figure 1 As shown. Magnesite itself possesses hydrophilic and oleophobic properties. Adding silicone oil and nano-hydrophobic silica can impart hydrophobicity to magnesite powder, reducing its hygroscopicity, preventing dry powder agglomeration, and thus extending its shelf life. Adding magnesium stearate and talc can improve the flowability and dispersion of magnesite powder, reducing its agglomeration, ultimately ensuring that all indicators of ordinary modified HM dry powder meet the national standards for dry powder fire extinguishing agents.

[0113] Example 4

[0114] (1) Preparation of ordinary magnesia ore powder: Natural magnesia ore was selected as raw material. The magnesia ore was placed in the Raymond mill bin and then crushed and refined by Raymond mill at a speed of 320 r / min for 60 min. After the process, it was vacuum freeze-dried and screened by air classifier to obtain ordinary magnesia ore powder with a particle size (D90) of less than 45 μm.

[0115] (2) Pre-dissolving the surface modifier: Sodium bicarbonate was pre-dissolved in deionized water to obtain a hydrolysis solution; it was fully dissolved by magnetic stirring for 0.5 h, and the temperature was maintained at 60℃ to accelerate the dissolution; the pH value was adjusted to 8.5 with deionized water.

[0116] (3) Impregnation and coating modification of ordinary magnesite powder (D90 < 45 μm): After step (2) is completed, the temperature is reduced to 50℃ and maintained throughout the process; the ordinary magnesite powder prepared in step (1) is added to the pre-hydrolysis solution in step (2), wherein the ordinary magnesite powder in step (1) and the surface modifier solution in step (2) are prepared according to the mass ratio of magnesite powder to dispersant deionized water of 1:5 and the mass ratio of sodium bicarbonate to magnesite powder of 20:100; the above mixture is placed in a hydraulic lifting high-speed disperser to disperse and obtain a dispersion liquid. The hydraulic high-speed disperser has a working power of 7.5kw, a total working time of 20min, a single working time of 8s, and a working interval of 10s; the dispersion liquid is uniformly stirred using a cantilever stirrer to obtain a suspension liquid; the rotation speed of the cantilever stirrer is 1200rpm and the stirring time is 6h;

[0117] (4) The suspension in (3) was placed in a refrigerated centrifuge for centrifugation. The speed of the refrigerated centrifuge was controlled at 3500 r / min, the temperature was controlled at -5℃, and the time was controlled at 10 min. After centrifugation, it was placed in a vacuum freeze dryer for freeze drying. The temperature was kept at -15℃ for 5 h to obtain the preliminary modified powder.

[0118] (5) Preparation of ordinary HM dry powder modified by impregnation and coating method: The preliminary modified powder obtained in step (4) is added to silicone oil, hydrophobic nano SiO2, magnesium stearate and talc powder for high-speed mixing. The mass ratio of modified magnesite powder, silicone oil, hydrophobic nano silica, magnesium stearate and talc powder is 100:1:3.5:3:2.5. The high-speed airflow mixer is controlled at a speed of 6000 r / min and kept for 5 min to reduce to the original particle size (D90 < 45 μm). After a second freeze-drying (vacuum freeze dryer temperature -10℃ for 12 hours), the finished ordinary modified HM dry powder is obtained.

[0119] Comparative Example 1

[0120] The method for preparing blank control samples is as follows:

[0121] (1) Preparation of blank ordinary magnesia ore powder: Natural magnesia ore was selected as raw material. The magnesia ore was placed in the Raymond mill bin and then crushed and refined by Raymond mill at a speed of 320 r / min for 60 min. After the process, the powder was freeze-dried under vacuum and screened by air classifier to obtain magnesia ore powder with a particle size (D90) of less than 45 μm.

[0122] (2) Preparation of blank ordinary magnesia powder: The magnesia powder obtained in step (1) is added to silicone oil, hydrophobic nano SiO2, magnesium stearate and talc powder and mixed at high speed. The mass ratio of magnesia powder, silicone oil, hydrophobic nano SiO2, magnesium stearate and talc powder is 100:1:3.5:3:2.5. The rotation speed is controlled at 8000 r / min and kept for 5 min to reduce to the original particle size (D90 < 35 μm). The product blank ordinary modified HM powder is obtained by second freeze drying (vacuum freeze dryer at -15℃ for 12 hours).

[0123] Comparative Example 2

[0124] The commercial ABC general dry powder was purchased from Jiangxi Jinxian Fire Protection Chemical Industry Co., Ltd.

[0125] Comparative Example 3

[0126] The method for preparing blank control potassium bicarbonate dry powder includes the following steps:

[0127] (1) Preparation of blank ordinary potassium bicarbonate particles: potassium bicarbonate (AR) was selected as raw material with an equivalent diameter of 0.5-1 mm. The potassium bicarbonate was placed in the Raymond mill hopper and then pulverized and refined by Raymond mill at a speed of 320 r / min for 60 min. After the process, the particles were freeze-dried under vacuum and screened by an air classifier to obtain ordinary potassium bicarbonate particles with a particle size (D90) of less than 45 μm.

[0128] (2) Preparation of blank ordinary potassium bicarbonate dry powder: The potassium bicarbonate particles obtained in step (1) are added to silicone oil, hydrophobic nano SiO2, magnesium stearate and talc powder and mixed at high speed. The mass ratio of potassium bicarbonate particles, silicone oil, hydrophobic nano SiO2, magnesium stearate and talc powder is 100:1:3.5:3:2.5. The rotation speed is controlled at 8000 r / min and kept for 5 min to reduce to the original particle size (D90 < 35 μm). The product blank ordinary potassium bicarbonate dry powder is obtained by second freeze drying (vacuum freeze dryer at -15℃ for 12 hours).

[0129] To verify the fire extinguishing effect of the ordinary modified HM dry powder provided in Example 1 above, the inventors used commercial ABC ordinary dry powder and blank HM ordinary dry powder as blank control samples to highlight the excellent fire extinguishing performance of the fire extinguishing agent developed in this patent.

[0130] Performance testing:

[0131] The experimental steps are as follows:

[0132] 1) Weigh 50g of commercial ABC ordinary dry powder, blank HM ordinary dry powder of Comparative Example 1 and modified HM ordinary dry powder prepared in Example 1 above for fire extinguishing experiment. Record the remaining mass after the fire extinguishing experiment, calculate the dry powder consumption and record the time used for fire extinguishing. Each group should be repeated at least three times and the average value should be taken.

[0133] 2) Using 0.2MPa nitrogen gas as the driving force, four different types of dry powder are released into the fire scene through nozzles directly above the fire source to extinguish the fire;

[0134] 3) Take 70ml of n-heptane and 80ml of distilled water and put them into a 200×200×40mm oil pan. Stir the oil-water mixture evenly and then ignite it with a lighter. Pre-ignite for 30 seconds to allow the flame to reach a stable state.

[0135] 4) The entire experimental process is as follows: Figure 2 The 1m shown 3 The experiment was conducted on a pressurized small-scale fire extinguishing experimental platform; the entire experiment was carried out in a manner similar to... Figure 2 The 1m shown 3 A pressurized small-scale fire extinguishing experimental platform (see Preparation and fire extinguishing mechanism of novel fire extinguishing powder based on recyclable struvite DOI:https: / / doi.org / 10.1016 / j.mtcomm.2023.105410)

[0136] Figure 2The specific test procedure is as follows: 50g of dry powder is placed in the pressure tank 1. The pressure is adjusted to 0.1MPa, 0.2MPa, and 0.3MPa using the nitrogen cylinder 7. The pressure values ​​are read from the pressure gauge 5. Each pressure group is repeated at least three times. The high-speed camera 2, data acquisition device 3 (temperature acquisition), flue gas analyzer 4, and K-type thermocouple 8 are then activated sequentially to record experimental data. 50ml of n-heptane and 70ml of water are poured into the oil pan 9. The fuel is ignited with an ignition gun and pre-burned for 30 seconds to allow the flame to stabilize. Then, the dry powder extinguishing agent is released using the nozzle 6. The release of the dry powder extinguishing agent is stopped after the flame is extinguished. The extinguishing time and dry powder consumption are recorded. One experiment is completed, and the next set of experiments is then conducted. The experiment is repeated at least three times under the same pressure.

[0137] 5) Verification experiment of impregnation-coating method for modified hydrated magnesite powder: The impregnation-coating method modified HM ordinary dry powder prepared in Example 1, blank HM ordinary dry powder, and commercial ABC ordinary dry powder were placed in the observation stage of a scanning electron microscope (Nanosem 430, FEI). The differences in appearance morphology of the three samples were observed using a scanning electron microscope (Nanosem 430, FEI). Figure 3 As shown.

[0138] from Figure 3 (a) It can be seen that after modification by impregnation and coating, potassium bicarbonate is uniformly loaded on the surface of the magnesite powder, compared with Figure 3 (b) The difference in fire extinguishing effect between the blank magnesite powder surface and the combined effect (as shown in Table 2) confirms the success of the impregnation and coating modification. The magnesite powder exhibits excellent physical inhibition effect, and the loading of potassium bicarbonate imparts a chemical inhibition effect, further improving the fire extinguishing efficiency. The chemical inhibition effect is the ability to capture combustion free radicals (hydrogen free radicals, oxygen free radicals, and hydroxyl free radicals), which can interrupt the chain reaction supporting combustion, thereby extinguishing the flame. The physical inhibition effect is the cooling effect on the fire scene, the dilution effect of the gases released by the thermal decomposition of dry powder on the oxygen concentration supporting combustion, and the suffocation effect of the dense oxide film formed by the final products of the thermal decomposition of dry powder. (Fire extinguishing time and dosage are shown in Table 2), achieving a fire extinguishing effect of 1+1>2.

[0139] 5) XRD (X-ray photoelectron diffraction) test: A BRUKER D8 X-ray diffractometer was used to test the HM ordinary dry powder modified by the impregnation and coating method prepared in Example 1. The test confirmed that potassium bicarbonate was successfully impregnated and coated onto the surface of the HM dry powder. Figure 4 As shown.

[0140] 6) Specific surface area (BET), pore size, and total volume (pore volume) testing: A Micro ASAP2460 adsorption-desorption instrument was used to test the adsorption-desorption curves of the impregnation-coating modified HM ordinary dry powder prepared in Example 1, the blank control HM ordinary dry powder, and the commercial ABC ordinary dry powder, and to obtain parameters such as specific surface area, pore size, and total volume (pore volume). Figure 5 As shown in Table 1.

[0141] Table 1 Comparison of Angle of Repose and Specific Surface Area of ​​Samples

[0142]

[0143] from Figure 5 As shown in Table 1, among the ordinary dry powders (D90 > 20 μm) prepared and purchased using the controlled variable method, the blank control HM ordinary dry powder and the KHCO3 / HM ordinary dry powder prepared in Example 1 have better parameters such as angle of repose and specific surface area than the commercial ABC ordinary dry powder. This further demonstrates the excellent commercial potential of HM dry powder in terms of production cost and ease of preparation process, although the specific surface area of ​​the modified Example 1 (31.405 m² / g) is smaller than that of the HM ordinary dry powder (35.885 m² / g). 2 / g), its total volume (0.138m 3 / g) is less than HM ordinary dry powder (0.147m 3 / g), the pore diameter (17.193nm) is larger than that of HM ordinary dry powder (16.637nm), but the impregnation and coating modification endows the HM dry powder in Example 1 with a chemical inhibition effect. The chemical inhibition effect has the ability to extinguish flames quickly. Combined with the excellent physical inhibition effect of HM dry powder, the combination of physical inhibition and chemical inhibition makes the overall fire extinguishing efficiency of KHCO3 / HM ordinary dry powder prepared in Example 1 better than that of blank control HM ordinary dry powder and commercial ABC ordinary dry powder.

[0144] 7) Explaining the extinguishing mechanism using TG-DSC: A STA449C simultaneous thermal analyzer was used to test the KHCO3 / HM ordinary dry powder from Example 1, the blank control HM ordinary dry powder, and the commercial ABC ordinary dry powder. TG, DTG, and DSC data were obtained and curves were plotted. The extinguishing mechanism was explained based on the data and the plotted curves, such as... Figure 6 As shown.

[0145] from Figure 6It can be seen that the impregnation and coating method modifies hydrated magnesite powder, lowering its pyrolysis temperature to around 120℃. The three peaks of the thermal decomposition rate are around 150℃, 250℃, and 450℃, respectively. The relatively dispersed pyrolysis temperature and thermal decomposition rate enable the capture of free radicals on the flame surface and the extinguishing of the flame root, ultimately achieving a dual inhibition effect of chemical and physical suppression, thus greatly improving the extinguishing efficiency of the modified dry powder. Differential scanning calorimetry shows that the entire pyrolysis process of the impregnation and coating method modified hydrated magnesite powder is an endothermic reaction, thus playing a role in cooling; the pyrolysis products CO2 and H2O play a role in diluting the oxygen concentration; the dense magnesium oxide film produced by pyrolysis provides a good suffocation and anti-reignition effect; the final product KOH of KHCO3 pyrolysis can capture flame free radicals and react with them. The entire pyrolysis process includes cooling, dilution, suffocation, and chemical inhibition, achieving faster and more rapid flame extinguishing.

[0146] 8) Screenshots of the fire extinguishing video, along with the extinguishing time and dosage, as shown below. Figure 7 As shown in Table 3, from Figure 7 As shown in Table 3, the modified magnesite powder prepared by the impregnation and coating method has the shortest extinguishing time (2.5s), followed by the blank control HM dry powder (3.1s), while the commercial ABC ordinary dry powder has a poor extinguishing effect (4.2s). The modified HM ordinary dry powder prepared in Examples 1-4 has a simple production process and low production cost, making it highly promising for commercial application.

[0147] 8) The temperature at the fire scene was collected using a temperature acquisition device and a type K thermocouple. Figure 8 As shown in Table 2, when the fire temperature reaches a stable state and the extinguishing agent is released, the KHCO3 / HM ordinary dry powder prepared in Example 1 has the most obvious cooling effect (208℃) within 10 seconds, followed by the unmodified blank control HM ordinary dry powder (197℃), while the commercial ABC ordinary dry powder has the worst cooling effect (191℃), which confirms that KHCO3 / HM ordinary dry powder has an excellent cooling effect.

[0148] 9) The CO concentration at the fire site was collected using a (testo350) flue gas analyzer. Figure 9 As shown in Table 2, the highest CO concentration of the KHCO3 / HM ordinary dry powder prepared in Example 1 after being released into the fire scene was 399 ppm. Compared with the unmodified blank control HM ordinary dry powder (433 ppm) and the commercial ABC ordinary dry powder (630 ppm), the KHCO3 modified HM dry powder has excellent smoke suppression effect.

[0149] Table 2 Comparison of sample temperature decrease and highest CO concentration

[0150]

[0151] The highest temperature in Table 2 is the highest temperature (outer flame temperature) detected by thermocouple #1 (the thermocouple closest to the outer flame of the fire).

[0152] Table 3 shows the performance tests of commercial ABC general dry powder and the dry powders of the three examples. D50 (μm) and D90 (μm) are the particle sizes corresponding to a cumulative particle size distribution percentage of 50% and 90%, respectively; bulk density (g / cm³) is also shown. 3 The term "compacted density" refers to the ratio of the mass m of a diffused powder to its filling volume V (including voids between powder particles) when there is no vibration. 3 Loose density (L) refers to the mass per unit volume of powder in a container after compaction under specified conditions. Loose density and compacted density are important indicators for evaluating the overall performance of powders, reflecting their overall performance. The smaller the difference between loose density and compacted density, the better the overall performance of the powder. Flowability (g / s) refers to the time required for a dry powder sample of a certain mass to flow through a standard funnel with a specified aperture. It is usually also measured by the angle of repose (as shown in Table 1) to measure the difference in flowability between dry powders. Contact angle (°) refers to the angle between the solid-liquid interface, through the liquid interior, and at the interface between the solid, liquid, and gas phases. It is an important measure of whether dry powder is wetted by other liquids. A contact angle greater than 90° indicates that its surface is not wetted by liquids and has hydrophobic properties.

[0153] Table 3. Comparison of performance parameters of the four examples with the blank control group: HM ordinary dry powder, commercial ABC ordinary dry powder, and potassium bicarbonate ordinary dry powder.

[0154]

[0155] As can be seen from Table 3, the fire extinguishing performance of the dry powder prepared in the four embodiments of the present invention is better than that of commercial ABC ordinary dry powder. The loose density, tapped density, flowability and contact angle of the dry powder in the four embodiments are comparable to or even better than those of commercial ABC ordinary dry powder.

[0156] The results of Comparative Example 1, Comparative Example 3 and Example 1 show that the fire extinguishing effect of potassium bicarbonate coating on the surface of magnesite powder in Example 1 is the best, and the two have a synergistic effect after potassium bicarbonate is coated on the surface of magnesite powder.

[0157] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A fire extinguishing powder based on hydromagnesite, characterized in that: The fire extinguishing powder comprises modified magnesite and dry powder additives; the modified magnesite powder is magnesite powder with a surface modifier; the modifier is selected from KHCO3. 3、 At least one of NaHCO3.

2. The fire extinguishing powder based on hydromagnesite according to claim 1, characterized in that: The extinguishing powder has a particle size D90 between 28-45 μm; and / or, The dry powder additive is silicone oil, hydrophobic nano-SiO2, magnesium stearate, and talc; and / or, In the modified magnesite powder, the mass ratio of the modifier to the magnesite powder is 10-20:

100.

3. The fire extinguishing powder based on hydromagnesite according to claim 2, characterized in that: The mass ratio of modified magnesite powder, silicone oil, hydrophobic nano-SiO2, magnesium stearate, and talc is 100:0.5-1:3.5-5:1.5-3:1-3.

5.

4. A method for preparing fire extinguishing powder based on hydromagnesite as described in any one of claims 1-3, characterized in that, Includes the following steps: Modified magnesite powder was mixed with dry powder additives, dried, and then fire extinguishing powder based on magnesite was obtained. The modified hydromagnesite powder is selected from at least one of the following: modified hydromagnesite powder prepared by wet impregnation of hydromagnesite powder in a modifier solution, and modified hydromagnesite powder prepared by dry coating of the modifier onto the surface of hydromagnesite powder.

5. The method for preparing fire extinguishing powder based on hydromagnesite according to claim 4, characterized in that: The dry powder additive is silicone oil, hydrophobic nano-SiO2, magnesium stearate, and talc; and / or, The magnesium stearate has a D90 of 5-10 μm; and / or, The talc powder has a D90 of 2.5-4 μm; and / or, The modified magnesite powder and dry powder additives are mixed evenly using a high-speed airflow mixer; and / or, The drying method is freeze drying.

6. The method for preparing fire extinguishing powder based on hydromagnesite according to claim 5, characterized in that: The hydrophobic nano-SiO2 has a D90 of 13-17 nm and a specific surface area of ​​250-350 m² / g; and / or, Control the speed of the high-speed airflow mixer to 6000-8000 r / min and maintain it for 5-10 minutes.

7. The method for preparing fire extinguishing powder based on hydromagnesite according to claim 4, characterized in that: The specific steps for preparing modified magnesite powder by wet impregnation of magnesite powder in a modifier solution include: (1-1) Add hydromagnesite powder to the modified aqueous solution and mix well to obtain a suspension; (1-2) The suspension is separated into solid and liquid, and the solid is dried to obtain modified hydromagnesite powder.

8. The method for preparing fire extinguishing powder based on hydromagnesite according to claim 7, characterized in that: The mass ratio of modifier to magnesite powder in the modifier aqueous solution is 10-20:100; and / or, The mass ratio of water in the aqueous solution of hydromagnesite powder and modifier is 0.8-1:5; and / or, The temperature for thorough mixing is 30-50℃; and / or, The pH value of the modifier aqueous solution is 8-10.

9. The method for preparing fire extinguishing powder based on hydromagnesite according to claim 8, characterized in that: Magnesia silicoides powder was added to an aqueous solution of a modifier and then dispersed in a hydraulic lifting high-speed disperser to obtain a dispersion. The hydraulic high-speed disperser had a working power of 7.5-9 kW, a total working time of 20-40 min, a single working time of 8-12 s, and a working interval of 10-20 s. The dispersion was then uniformly stirred using a cantilever agitator to obtain a suspension. The cantilever agitator had a rotation speed of 1200-1500 rpm and a stirring time of 6-8 h. The preparation method of the modifier aqueous solution includes the following steps: The modifier is first fully dissolved in deionized water to obtain a hydrolysis solution. After complete dissolution, the pH value is adjusted to 8-10.

10. The method for preparing fire extinguishing powder based on hydromagnesite according to claim 9, characterized in that: The method for complete dissolution is to stir under heating conditions, with a heating temperature of 50-60℃ and a stirring time of 0.5-1h.

11. The method for preparing fire extinguishing powder based on hydromagnesite according to claim 7, characterized in that: The solid-liquid separation method for suspensions is centrifugation; and / or, The drying method is freeze drying.

12. The method for preparing fire extinguishing powder based on hydromagnesite according to claim 11, characterized in that: The solid-liquid separation method for suspensions is centrifugation in a refrigerated centrifuge; and / or, The drying method is freeze drying in a vacuum freeze dryer.

13. The method for preparing fire extinguishing powder based on hydromagnesite according to claim 12, characterized in that: The refrigerated centrifuge is controlled with a rotation speed of 3000-5000 r / min, a temperature of (-5)-(-10)℃, and a time of 8-10 min; and / or, The freeze-drying temperature is (-10)-(-20)℃, and the temperature is maintained for 4-6 hours to obtain modified hydromagnesite powder.

14. The method for preparing fire extinguishing powder based on hydromagnesite according to claim 4, characterized in that: The specific steps for preparing modified magnesite powder by dry coating a modifier onto the surface of magnesite powder include: Magnesite powder was placed in a coating and modification machine hopper, then a modifier was added for coating and modification, and dried to obtain modified magnesite powder.

15. The method for preparing fire extinguishing powder based on hydromagnesite according to claim 14, characterized in that: The mass ratio of modifier to hydrated magnesite powder is 10-20:100; and / or, The equivalent diameter of the modifier is 0.5-1 mm; and / or, The coating modification machine has a working power of 4-6 kW and a coating time controlled at 30-50 min; and / or, The drying method is freeze drying.

16. The method for preparing fire extinguishing powder based on hydromagnesite according to claim 4, characterized in that: The hydromagnesite powder is selected from hydromagnesite powder with a particle size D90 of less than 45μm.

17. The method for preparing fire extinguishing powder based on hydromagnesite according to claim 16, characterized in that: The preparation method of hydromagnesia ore powder includes using natural hydromagnesia ore as raw material, refining the powder, vacuum freeze drying, and sieving the hydromagnesia ore powder with a particle size D90 of less than 45μm using an air classifier.

18. The method for preparing fire extinguishing powder based on hydromagnesite according to claim 17, characterized in that: The equivalent diameter of the natural hydromagnesite is 200 mm, and the purity is ≥98%; and / or, Natural hydromagnesite ore was pulverized and refined using a Raymond mill, with the rotation speed controlled at 320-400 r / min and the time controlled at 60-120 min.

19. The application of the fire extinguishing powder based on hydromagnesite as described in any one of claims 1-3 in fire extinguishing.

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