Low-sulfur carbonate tailings-based dry powder fire extinguishing agent, preparation method and application thereof

Abstract

The application discloses a low-sulfur carbonate tailing-based dry powder fire extinguishing agent and a preparation method and application thereof, and comprises low-sulfur carbonate tailing powder and a fire extinguishing synergist, wherein the low-sulfur carbonate tailing powder is obtained by drying and superfine crushing of low-sulfur tailings; the low-sulfur tailings are low-sulfur tailings with a water content of less than or equal to 1.0%, a carbonate mineral component content of more than 15% and a sulfur content (calculated in terms of SO3) of less than 2%; and the fire extinguishing synergist comprises triethanolamine, sodium polyacrylate, and sodium hexametaphosphate and / or sodium tripolyphosphate. The application breaks through the single mode of relying on physical covering of the existing tailing-based fire extinguishing agent, and breaks through the use limitation of triethanolamine, sodium polyacrylate and sodium hexametaphosphate as grinding aids in the prior art. The application reconfigures the above components into a fire extinguishing synergist, so that the fire extinguishing synergist and the low-sulfur carbonate tailing form a time sequence synergistic fire extinguishing effect in a high-temperature fire scene.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, specifically to a low-sulfur carbonate tailings-based dry powder fire extinguishing agent, its preparation method, and its application. Background Technology

[0002] The mining and beneficiation processes generate a large amount of tailings solid waste. Its accumulation not only occupies land resources but also easily leads to environmental problems such as soil erosion, soil pollution, and dust pollution, hindering the green development of the mining industry. Therefore, exploring high-value-added resource utilization pathways for tailings is of great significance for achieving sustainable mine development under the "dual carbon" target.

[0003] In the field of fire protection, dry powder extinguishing agents are widely used due to their high extinguishing efficiency and wide applicability. However, traditional ABC-type dry powder extinguishing agents (such as ammonium phosphate) are mainly based on chemically synthesized raw materials, which have problems such as high raw material costs, high production energy consumption, strong adhesion of residues after extinguishing that are difficult to clean, and phosphates that can easily cause eutrophication of water bodies.

[0004] To integrate solid waste utilization with firefighting technology, existing technologies have reported the use of tailings to prepare fire extinguishing agents. For example, Chinese invention patent CN111420338B discloses a method for preparing fire extinguishing agents using quartz sand tailings. This method mainly relies on the physical covering effect of high-silica tailings for fire extinguishing, resulting in a simple extinguishing mechanism, limited resistance to reignition, and the need to compound a large amount of other chemical raw materials. Furthermore, Chinese invention patents CN116273416B and CN115449348B disclose grinding aids or milling agents containing triethanolamine, sodium polyacrylate, and sodium hexametaphosphate, respectively, and their use in the grinding of non-metallic minerals such as calcium carbonate and brucite. However, in these existing technologies, triethanolamine, sodium polyacrylate, and sodium hexametaphosphate are only used as physical grinding aids. Their technical purpose is to improve grinding efficiency, prevent particle agglomeration, and reduce energy consumption. They do not reveal that these components can undergo chemical synergistic effects with carbonate minerals under high-temperature fire conditions, nor do they apply them to the field of fire extinguishing agents.

[0005] On the other hand, while existing ultrafine dry powder fire extinguishing agents (such as those specified in XF 578-2023 standard, which stipulates that 90% of the particles should be ≤15μm) have good dispersibility, they generally suffer from problems such as excessively large specific surface area, strong hygroscopicity, easy agglomeration during long-term storage, and poor stability. Meanwhile, conventional dry powders with excessively large particle sizes (>50μm) have rapid settling speed, poor diffusion, and low fire extinguishing efficiency. Furthermore, some sulfur-containing tailings or sulfur-containing fire extinguishing agents are prone to producing toxic gases such as sulfur dioxide at high temperatures, limiting their application in confined spaces such as mines and tunnels.

[0006] Therefore, there is an urgent need to develop a highly efficient and environmentally friendly fire extinguishing agent that can fully utilize the mineral chemical properties of tailings, requires no large-scale chemical compounding, has a simple process, low cost, good storage stability, and is suitable for confined spaces. Summary of the Invention

[0007] The purpose of this invention is to provide a low-sulfur carbonate tailings-based dry powder fire extinguishing agent, its preparation method, and its application, in order to solve the technical problems of existing tailings-based fire extinguishing agents having a single fire extinguishing mechanism, poor storage stability of traditional ultrafine dry powder, and sulfur-containing fire extinguishing agents being unsuitable for confined spaces.

[0008] This invention targets low-sulfur carbonate tailings containing ≥15% carbonate mineral components and <2% sulfur content (as SO3). By reconstructing the synergistic relationship between tailings powder and trace additives, it transforms the traditional "grinding aid / dispersant" into a "fire extinguishing synergist." By controlling a specific particle size range, the fire extinguishing agent possesses multiple fire extinguishing mechanisms, including wide-temperature-range continuous endothermic decomposition, gas-phase inert gas dilution, high-temperature vitrification oxygen isolation, and catalytic char formation.

[0009] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a low-sulfur carbonate tailings-based dry powder fire extinguishing agent, comprising low-sulfur carbonate tailings micro powder and a fire extinguishing synergist, wherein the amount of the fire extinguishing synergist added is 0.2-0.5% of the mass of the low-sulfur carbonate tailings micro powder, wherein the low-sulfur carbonate tailings micro powder is obtained by drying and ultra-fine grinding of low-sulfur tailings; wherein the low-sulfur tailings are low-sulfur tailings containing >15% carbonate mineral components and <2% sulfur content (calculated as SO3); wherein the fire extinguishing synergist includes triethanolamine, sodium polyacrylate, and at least one selected from sodium hexametaphosphate and sodium tripolyphosphate; wherein the particle size of the low-sulfur carbonate tailings micro powder is 10μm~50μm, and the moisture content of the micro powder is ≤0.25%.

[0010] In some embodiments, the amount of triethanolamine added is 0.02-0.05% of the mass of the low-sulfur carbonate tailings powder, the amount of sodium polyacrylate added is 0.1-0.2% of the mass of the low-sulfur carbonate tailings powder, and the amount of sodium hexametaphosphate and / or sodium tripolyphosphate added is 0.1-0.2% of the mass of the low-sulfur carbonate tailings powder.

[0011] In some embodiments, the carbonate mineral includes one or more of dolomite, ferrodolite, siderite, and magnesite.

[0012] In some embodiments, the ferrodolomite and / or siderite constitute ≥5% of the mass fraction of the low-sulfur tailings.

[0013] Secondly, the present invention provides a method for preparing a low-sulfur carbonate tailings-based dry powder fire extinguishing agent, comprising the following steps: Step 1: Raw material screening and pretreatment: Select low-sulfur carbonate tailings, wherein the mass content of carbonate mineral components in the tailings is ≥15% and the sulfur content (as SO3) is <2%; remove impurities from the tailings to obtain pretreated tailings; Step 2: Drying treatment: Dry the pretreated tailings at a temperature of 105℃~120℃ to obtain dry tailings with a moisture content of ≤1.0%. Step 3, Co-grinding and synergistic activation: The dried tailings and the fire extinguishing synergist are placed together in a planetary ball mill for grinding. The particle size of the tailings powder after grinding is controlled to be 10μm~50μm and the moisture content is ≤0.25%, so as to obtain the low-sulfur carbonate tailings-based dry powder fire extinguishing agent.

[0014] In some embodiments, in step one, the impurities include stones, wood chips, and metal scraps.

[0015] In some embodiments, in step three, the ball-to-material ratio of the planetary ball mill is (4~8):1, the grinding speed is 300~500 r / min, and the grinding time is 1~4 h.

[0016] Thirdly, the present invention provides an application of a low-sulfur carbonate tailings-based dry powder extinguishing agent in the field of fire fighting. The extinguishing agent is filled in the form of dry powder in a pressurized dry powder fire extinguisher and uses an inert gas (such as nitrogen or carbon dioxide) as the propellant gas.

[0017] In some embodiments, the fire extinguishing is for fires in enclosed spaces such as mines, tunnels, underground utility tunnels, or cable trenches.

[0018] Based on the above technical solution, the embodiments of the present invention can produce at least the following technical effects: (1) The synergistic fire extinguishing mechanism of fire extinguishing synergist and carbonate tailings. This invention breaks through the single mode of existing tailings-based fire extinguishing agents that rely solely on physical coverage, and also breaks through the limitation of existing technologies in which triethanolamine, sodium polyacrylate, and sodium hexametaphosphate are only used as grinding aids. This invention reconstructs the above components into a fire extinguishing synergist, enabling it to form a time-sequential synergistic fire extinguishing effect with low-sulfur carbonate tailings in high-temperature fires: Gas-phase chemical inhibition: Dolomite, magnesite, siderite and other multi-carbonates in the tailings undergo continuous thermal decomposition in a wide temperature range of 350℃~800℃, absorbing a large amount of heat and releasing CO2; triethanolamine volatilizes and decomposes at high temperature, releasing nitrogen-containing inert gases, which further dilute the oxygen concentration in the combustion zone. Solid-phase physical isolation and vitrification oxygen barrier: The original SiO2 and refractory oxides such as CaO, MgO, and Fe2O3 generated from the decomposition of carbonates in the tailings can form a covering layer on the surface of the combustibles; at the same time, sodium hexametaphosphate and / or sodium tripolyphosphate react with Ca²⁺ in the tailings at high temperatures. + Mg² + Fe² + / Fe³ + The reaction produces a dense phosphate glass layer, which significantly enhances the oxygen barrier effect; Catalytic char formation enhances oxygen barrier: For FeCO3-containing iron dolomite and / or siderite tailings, the iron oxides produced by their thermal decomposition have a catalytic char formation effect, which can promote the formation of a dense char layer on the surface of combustibles; sodium polyacrylate can also promote the formation of residual char at high temperatures, which together with the phosphate glass layer constitute a strong heat insulation and oxygen barrier.

[0019] (2) Achieving a balance between fire extinguishing efficiency and storage stability with a "golden particle size" of 10μm~50μm. Existing ultrafine dry powder (<15μm) has good initial dispersibility, but it suffers from severe moisture absorption and agglomeration, and its spraying performance decreases significantly after long-term storage; while powder with a particle size >50μm settles too quickly and is difficult to effectively suspend in the flame zone. This invention confirms through Table 1 and storage stability comparison experiments that controlling the particle size of low-sulfur carbonate tailings micro powder to 10μm~50μm (preferably 15μm~35μm) can match the thermal decomposition rate of carbonate minerals with the flame propagation rate, achieving a time-sequential synergy of "solid phase heat absorption and oxygen isolation + gas phase CO2 dilution", while effectively avoiding the problem of moisture absorption and agglomeration of ultrafine powder, and has excellent long-term storage stability.

[0020] (3) The low sulfur content makes it safe for use in confined spaces. This invention strictly limits the sulfur content (calculated as SO3) in tailings to <2%, which avoids the generation of high-temperature SO2 toxic gas during the fire extinguishing process from the source. This makes the fire extinguishing agent particularly suitable for fire fighting in confined or semi-confined spaces such as mines, tunnels, and underground pipe corridors, and solves the safety hazard of personnel poisoning when using sulfur-containing fire extinguishing agents in confined spaces.

[0021] (4) Disaster relief using waste, with extremely low cost and simple process. This invention directly uses stockpiled low-sulfur carbonate tailings as the main material, with raw material cost of almost zero; the preparation process only requires low-temperature drying and co-grinding activation, without the need for high-temperature calcination or complex chemical synthesis, the process is simple, energy consumption is low, and it is easy to industrialize. Detailed Implementation

[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0023] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0025] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0026] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0027] The moisture content of the dried tailings was calculated using the standard drying method.

[0028] Particle size D 50 Particle size was measured using a Bettersize2600 laser particle size analyzer.

[0029] Example 1: Basic Synergistic Formula (1) Raw material screening and pretreatment: Low-sulfur tailings from a mine were selected. XRD and chemical analysis showed that the mass content of carbonate minerals (16% dolomite, 12% siderite, and 3% magnesite, totaling 31%) in the tailings was 31%, the sulfur content (as SO3) was 0.9%, and the remainder was mainly quartz and a small amount of silicate minerals. Large impurities such as stones, wood chips, and metal fragments were removed by screening to obtain pretreated tailings.

[0030] (2) Drying treatment: The pretreated tailings are placed in an oven and the drying temperature is controlled at 110℃. The tailings are dried at a constant temperature until the moisture content is 0.8% to obtain dried tailings.

[0031] (3) Co-grinding and synergistic activation: The dried tailings were placed in a planetary ball mill, and triethanolamine was added at 0.02% of the mass of the dried tailings, sodium polyacrylate at 0.15%, and sodium hexametaphosphate at 0.15%. The ball-to-material ratio was set to 6:1, the grinding speed was 400 r / min, and the grinding time was 2.5 h. After grinding, the particle size D was obtained. 50 The ultrafine tailings powder with a particle size of 28 μm and a moisture content of 0.20% is the dry powder fire extinguishing agent of this invention, denoted as sample S1.

[0032] Example 2: Optimized formula rich in iron-rich dolomite (1) Raw material screening and pretreatment: Low-sulfur lead-zinc tailings from another mining area were selected, in which the mass content of iron dolomite (CaFe(CO3)2) was 18%, the content of dolomite was 12%, the content of siderite was 5%, the total content of carbonate minerals was 35%, and the sulfur content (calculated as SO3) was 0.6%. After removing impurities, pretreated tailings were obtained.

[0033] (2) Drying treatment: The drying temperature is 115℃, and the moisture content after drying is 0.5%.

[0034] (3) Co-grinding and synergistic activation: Triethanolamine was added at 0.05% of the mass of dried tailings, sodium polyacrylate at 0.2% and sodium tripolyphosphate at 0.2%. The ball-to-material ratio was 6:1, the rotation speed was 450 r / min, and the grinding was carried out for 3 h. The particle size D was obtained. 50 The micro powder with a diameter of 22 μm and a moisture content of 0.18% is designated as sample S2.

[0035] Example 3: Wide-range particle size validation formulation (1) Raw material screening and pretreatment: Same as in Example 1.

[0036] (2) Drying treatment: drying temperature 120℃, moisture content 0.6%.

[0037] (3) Co-grinding and synergistic activation: Triethanolamine was added at 0.03% of the mass of dried tailings, sodium polyacrylate at 0.1% and sodium hexametaphosphate at 0.1%. The grinding time was adjusted to 1.5 h to obtain a particle size D. 50 The micro powder with a diameter of 42 μm is designated as sample S3.

[0038] Comparative Example 1: Tailings powder without added fire extinguishing synergist Using the same low-sulfur carbonate tailings raw material and the same drying and grinding process as in Example 1, but without adding triethanolamine, sodium polyacrylate, and sodium hexametaphosphate, the material was ground to a similar particle size (D). 50 (Approximately 30 μm), denoted as D1.

[0039] Comparative Example 2: Quartz sand tailings fire extinguishing agent containing only a single dispersant Following the method in CN111420338B, quartz sand tailings (SiO2 content >90%, almost no carbonate) were used. Sodium hexametaphosphate was added as a dispersant at 0.3% of the dry tailings mass. The fire extinguishing agent was prepared by the same drying and grinding process and denoted as D2.

[0040] Comparative Example 3: Traditional ABC dry powder fire extinguishing agent Commercially available ammonium phosphate ABC dry powder fire extinguishing agent (main content ≥75%) was selected and designated as D3.

[0041] Comparative Example 4: Ultrafine particle size (<10μm) carbonate tailings powder Using the same raw materials and additives as in Example 1, but extending the grinding time to 6 hours, a particle size D was obtained. 50 The micro powder with a particle size of 8 μm is designated as D4.

[0042] Comparative Example 5: Coarse-grained (>50μm) carbonate tailings powder Using the same raw materials and additive formulation as in Example 1, but shortening the grinding time to 0.5 h, a particle size D was obtained. 50 The micro powder with a particle size of 75 μm is designated as D5.

[0043] Fire extinguishing performance and mechanism verification experiment 1. Fire Extinguishing Efficiency Comparison Test Samples S1-S3 and comparative examples D1-D5 were filled into portable dry powder fire extinguisher cylinders of the same specifications (3 kg filling capacity) and pressurized to 1.2 MPa with nitrogen. A standard Class B oil pan fire model was established according to relevant standards (using a square oil pan, area 0.25 m², height 100 mm, wall thickness 6 mm, bottom 600 mm from the ground. The fuel was commercial-grade n-heptane, 12.5 L, with water at the bottom, the liquid level 50 mm from the top edge of the oil pan, and a pre-ignition time of 30 s). The main test indicators were: extinguishing time, reignition resistance time, and extinguishing agent dosage.

[0044] Table 1 Fire extinguishing performance test results

[0045] The fire extinguishing efficiency of S1~S3 is significantly better than that of D1, D2 and D5, and comparable to or better than that of D3. However, the storage stability of S1~S3 (caking rate and ejection rate after 6 months and 12 months of accelerated aging) is significantly better than that of D4.

[0046] 2. High-Temperature Synergistic Mechanism Verification Experiment (1) TG-DSC analysis: Thermogravimetric-differential scanning calorimetry (TG-DSC) was performed on the raw materials of Example 1. The test conditions were: nitrogen atmosphere, flow rate 50 mL / min, heating rate 10℃ / min, and temperature range of room temperature to 900℃. The analysis results are shown in Table 2. The wide-temperature-range continuous endothermic decomposition characteristics of dolomite (~750℃), siderite (~400℃), and magnesite (~350℃) were demonstrated.

[0047] Table 2. Characteristic parameters of TG-DSC thermal analysis of tailings raw material in Example 1

[0048] The above results indicate that the three main carbonate minerals in the tailings used in Example 1 achieved sustained heat absorption and CO2 release over a wide temperature range, providing a continuous material and energy basis for subsequent gas-phase dilution and solid-phase vitrification reactions.

[0049] (2) SEM-EDS analysis of extinguishing residues: Scanning electron microscopy and energy dispersive spectroscopy were performed on the residues after extinguishing S1, S2 and D1 (accelerating voltage 15 kV, working distance 10 mm, average of several points). The surface elemental composition and macroscopic morphology are shown in Table 3.

[0050] Table 3 Elemental Analysis (EDS) and Morphological Characteristics of Extinguishing Residue Surface

[0051] Note: The elemental content in the table is the mass percentage obtained from EDS energy dispersive spectroscopy; EDS has errors in the quantitative analysis of light elements such as carbon and oxygen, and the results are only used for relative comparison between samples; the detection area is the surface layer of fire extinguishing residue.

[0052] As shown in Table 3: The phosphorus (P) content on the surface of S1 and S2 residues was as high as 8.6% and 12.1%, respectively, while the phosphorus content on the surface of D1 was only 0.4% (close to the background of the raw materials). This proves that sodium hexametaphosphate / sodium tripolyphosphate migrated and accumulated on the surface of the combustibles at high temperature, forming a dense phosphate-containing layer. - The surface iron (Fe) content (8.5%) of S2 is significantly higher than that of S1 (4.2%), and the carbon (C) content reaches 7.2%. Combined with its "dark gray-black" and "closed bubble structure" morphology, it is confirmed that the iron oxide produced by the decomposition of iron dolomite / siderite catalyzes the generation of residual carbon, and together with the phosphate glass layer, it forms a composite oxygen barrier. The D1 surface is dominated by silicon (Si) (29.2%), with very low levels of phosphorus and carbon. It exhibits a loosely packed morphology, consisting only of physical covering, without glassization or carbonization characteristics.

[0053] (3) Toxicity test of smoke in confined space: In a 10m³ standard confined combustion chamber, after extinguishing a 0.25m² oil pan fire with 3kg of extinguishing agent, the peak concentration of SO2 in chamber S1 (SO3=0.6%) was 45 mg / m³ within 30s, while the peak concentration of sulfur tailings extinguishing agent (SO3=3%) was 480 mg / m³. The former is lower than the occupational exposure limit specified in GBZ 2.1-2019 (5mg / m³ is MAC, or 10mg / m³ is PC-TWA, depending on the specific standard), while the latter seriously exceeds the limit.

[0054] (4) Screening experiment of synergistic agents: The fire extinguishing efficiency of adding triethanolamine alone, sodium polyacrylate alone, sodium hexametaphosphate alone, binary combination and ternary combination (S1 formula) were compared. Comparative Example 6: Monotriethanolamine Unlike Example 1, (3) only 0.302% triethanolamine was added in co-grinding and synergistic activation, and sodium polyacrylate and sodium hexametaphosphate were not added. The other conditions were the same as in Example 1.

[0055] Comparative Example 7: Sodium Monopolyacrylate Unlike Example 1, (3) only 0.302% sodium polyacrylate was added in co-grinding and synergistic activation, without adding triethanolamine and sodium hexametaphosphate, and the other conditions were the same as in Example 1.

[0056] Comparative Example 8: Sodium hexametaphosphate Unlike Example 1, (3) only 0.302% sodium hexametaphosphate was added in co-grinding and synergistic activation, without adding triethanolamine and sodium polyacrylate, and the other conditions were the same as in Example 1.

[0057] Comparative Example 9: Triethanolamine and Sodium Polyacrylate Unlike Example 1, (3) 0.02% triethanolamine and 0.30% sodium polyacrylate were added for co-grinding and synergistic activation, but sodium hexametaphosphate was not added, and the other conditions were the same as in Example 1.

[0058] Comparative Example 10: Sodium polyacrylate and sodium hexametaphosphate Unlike Example 1, (3) co-grinding and synergistic activation added 0.151% sodium polyacrylate and 0.151% sodium hexametaphosphate, but not triethanolamine, and the other conditions were the same as in Example 1.

[0059] Comparative Example 11: Triethanolamine and Sodium Hexametaphosphate Unlike Example 1, (3) 0.02% triethanolamine and 0.30% sodium hexametaphosphate were added for co-grinding and synergistic activation, but sodium polyacrylate was not added, and the other conditions were the same as in Example 1.

[0060] Table 4 Fire Extinguishing Performance Test Results

[0061] The above data is the average of three repeated experiments.

[0062] As shown in Table 4, the extinguishing time of single additives (Comparative Examples 6-8) or binary combinations (Comparative Examples 9-11) is over 9 seconds, while the ternary combination in Example 1 shortens the extinguishing time to 3-5 seconds, exhibiting a significant non-linear synergistic effect of "1+1+1>3". The extinguishing synergist and carbonate tailings form a "three-in-one" synergistic extinguishing mechanism. This invention breaks through the single mode of existing tailings-based fire extinguishing agents that rely solely on physical coverage, and also overcomes the limitation of existing technologies where triethanolamine, sodium polyacrylate, and sodium hexametaphosphate are only used as grinding aids.

[0063] The sodium hexametaphosphate and sodium tripolyphosphate described in this invention are not merely used as physical dispersants, but rather undergo an in-situ chemical reaction with the thermal decomposition products of low-sulfur carbonate tailings under high-temperature fire conditions to generate a dense phosphate glass layer, achieving solid-phase oxygen isolation. The reaction mechanism is as follows: (1) High-temperature melting and chemical activation of sodium hexametaphosphate Sodium hexametaphosphate melts rapidly in the high-temperature zone (>600℃), transforming into a highly reactive polyphosphate melt. Simultaneously, carbonate minerals such as dolomite, siderite, and magnesite in the tailings decompose, releasing basic oxides such as CaO, MgO, and Fe2O3 / FeO. The molten sodium hexametaphosphate undergoes an acid-base reaction with these metal oxides, generating glass network precursors such as calcium metaphosphate and magnesium metaphosphate, while simultaneously releasing low-melting-point Na2O (part of the Na produced during melting). + Volatilize (in the form of Na₂O or Na vapor), leaving Na + As a monovalent network-modifying ion, it breaks POP bridging bonds and reduces melt viscosity; for Fe³⁺-containing... + / Fe² + System, Fe³ + As a network intermediate, it can be embedded in network gaps as a modifier, or it can partially replace P in [FeO4] tetrahedra to participate in network formation; Fe² + Primarily used as a network modifier embedded in network gaps; (2) Formation of glass network structure Under high-temperature (800℃~1000℃) flame conditions, the above reaction products do not exist in independent crystalline form, but rather form a continuous three-dimensional network structure through the condensation of P–O–M bonds (M = Ca, Mg, Fe), i.e., phosphate glass. PO4 tetrahedrons act as glass network forgings, Ca² + Mg² + Fe³ + / Fe²+ Na is embedded in network gaps as a network modifier. + Na₂O partially evaporates and partially remains in the network, reducing the viscosity of the glass and allowing the melt to spread rapidly on the surface of the burning material during the fire extinguishing process. After the fire is extinguished, the temperature drops sharply, and the melt quickly solidifies into a dense, continuous, and crack-free phosphate glass-metal oxide composite layer with low thermal conductivity (typically <1 W / (m·K)) and almost no air permeability, thus effectively preventing the transfer of oxygen and heat to the combustible matrix.

[0064] (3) Synergistic vitrification effect of sodium tripolyphosphate Sodium tripolyphosphate (Na5P3O) 10 After being melted at high temperature, the chain triphosphate further condenses into chain polyphosphate (n>3), and finally reacts with CaO / MgO to generate a mixture of pyrophosphate and metaphosphate, which is then melted into the phosphate glass network of the CaO-MgO-P2O5-Na2O system.

[0065] (4) Temporal synergy with carbonate tailings decomposition This vitrification process closely matches the wide-temperature-range decomposition of multi-component carbonates in the tailings, forming a "self-supplied" in-situ reaction system: 350℃~500℃: Magnesite and siderite decompose first, providing initial MgO and Fe2O3, promoting pre-oxidation and early carbonization; 620℃-650℃: Sodium hexametaphosphate and sodium tripolyphosphate begin to soften and melt, their viscosity decreases, and they become spreadable; 750℃~800℃: Dolomite decomposes in large quantities, releasing CaO and MgO, providing sufficient network modifier ions for the glass network; >800℃: Molten phosphate and Ca²⁺ + / Mg² + / Fe³ + It reacts fully and spreads on the surface of the burning material, then rapidly cools and solidifies into a dense glass shell after the fire is extinguished.

[0066] Thus, this invention constructs a solid barrier on the surface of combustibles with both physical isolation and chemical stability through a synergistic mechanism of "continuous alkali supply of carbonates + polyphosphate melting and film formation + cross-linking and vitrification of multiple metal ions", which significantly improves the anti-reignition performance.

[0067] (5) Storage stability verification experiment To further verify the advantages of 10μm~50μm particle size in storage stability, accelerated aging experiments were conducted on S1, S2, and D4. The experimental conditions followed the relevant test methods in GB 4066-2017 "Dry Powder Fire Extinguishing Agents": temperature 40℃±2℃, relative humidity 75%±5%, and storage period of 6 months. The test results are shown in Table 5.

[0068] Table 5 Results of Accelerated Aging Storage Stability Test

[0069] As shown in Table 5, D4 (ultrafine powder) with a particle size <10μm has an excessively large specific surface area and extremely high hygroscopicity. After 6 months of simulated storage, the agglomeration rate is as high as 68.5%, and it has lost its actual fire extinguishing ability. On the other hand, S1 and S2, which are in the range of 10μm to 50μm, have a moisture content that is always controlled at an extremely low level and a spray rate >95%, which proves that the particle size range defined by the present invention perfectly balances fire extinguishing efficiency and long-term storage stability.

[0070] The scope of protection of this invention is defined by the claims. The above embodiments are only used to explain this invention and are not intended to limit this invention. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the inventive concept of this invention, and these all fall within the scope of protection of this invention.

Claims

1. A low-sulfur carbonate tailings-based dry powder fire extinguishing agent, characterized in that, The product comprises low-sulfur carbonate tailings micronized powder and a fire extinguishing synergist. The fire extinguishing synergist is added at a rate of 0.2-0.5% of the mass of the low-sulfur carbonate tailings micronized powder. The low-sulfur carbonate tailings micronized powder is obtained by drying and ultra-fine grinding low-sulfur tailings. The low-sulfur tailings are low-sulfur tailings containing >15% carbonate mineral components and <2% sulfur content (calculated as SO3). The fire extinguishing synergist includes triethanolamine, sodium polyacrylate, and at least one selected from sodium hexametaphosphate and sodium tripolyphosphate. The particle size of the low-sulfur carbonate tailings micronized powder is 10μm~50μm, and the moisture content of the powder is ≤0.25%.

2. The low-sulfur carbonate tailings-based dry powder fire extinguishing agent according to claim 1, characterized in that, The amount of triethanolamine added is 0.02-0.05% of the mass of the low-sulfur carbonate tailings powder, the amount of sodium polyacrylate added is 0.1-0.2% of the mass of the low-sulfur carbonate tailings powder, and the amount of sodium hexametaphosphate and / or sodium tripolyphosphate added is 0.1-0.2% of the mass of the low-sulfur carbonate tailings powder.

3. The low-sulfur carbonate tailings-based dry powder fire extinguishing agent according to claim 1, characterized in that, The carbonate minerals include one or more of dolomite, ferrodolite, siderite, and magnesite.

4. The low-sulfur carbonate tailings-based dry powder fire extinguishing agent according to claim 3, characterized in that, The iron dolomite and / or siderite account for ≥5% of the mass fraction of the low-sulfur tailings.

5. A method for preparing a low-sulfur carbonate tailings-based dry powder fire extinguishing agent, characterized in that, Includes the following steps: Step 1: Raw material screening and pretreatment: Select low-sulfur carbonate tailings, wherein the mass content of carbonate mineral components in the tailings is >15% and the sulfur content (as SO3) is <2%; remove impurities from the tailings to obtain pretreated tailings; Step 2: Drying treatment: Dry the pretreated tailings at a temperature of 105℃~120℃ to obtain dry tailings with a moisture content of ≤1.0%. Step 3, Co-grinding and synergistic activation: The dried tailings and the fire extinguishing synergist are placed together in a planetary ball mill for grinding. The particle size of the tailings powder after grinding is controlled to be 10μm~50μm and the moisture content is ≤0.25%, so as to obtain the low-sulfur carbonate tailings-based dry powder fire extinguishing agent.

6. The method according to claim 5, characterized in that, In step one, the impurities include stones, wood chips, and metal scraps.

7. The method according to claim 5, characterized in that, In step three, the ball-to-material ratio of the planetary ball mill is (4~8):1, the grinding speed is 300~500 r / min, and the grinding time is 1~4 h.

8. The application of the extinguishing agent prepared according to any one of claims 5-7 in the field of fire fighting, characterized in that, The extinguishing agent is filled in the form of dry powder in a pressurized dry powder fire extinguisher, and an inert gas (such as nitrogen or carbon dioxide) is used as the propellant.

9. The application according to claim 8, characterized in that, The fire extinguishing refers to fires in enclosed spaces such as mines, tunnels, underground pipe corridors, or cable trenches.

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