Gypsum-based ecological flame-retardant material for forest fire isolation belt and preparation method thereof

Abstract

The invention discloses a gypsum-based ecological flame-retardant material for a forest fire isolation belt and a preparation method of the gypsum-based ecological flame-retardant material, and relates to the technical field of forest fire control. Comprising building gypsum, a flame-retardant synergist, red soil, natural water-retaining minerals, a water-retaining agent, a plant nutrient agent, a microbial agent, a retarder and water, calcium sulfate dihydrate formed after the building gypsum is hydrated has the advantages of low thermal conductivity and heat absorption in the crystal water removal process, the flame-retardant synergist is supplemented, and the red soil and the natural water-retaining minerals are matched, so that the heat-retaining property of the building gypsum is improved; the gypsum-based ecological flame-retardant material prepared by adding a plant nutrient agent, a water-retaining agent, a microbial agent and a retarder can be used for flame retardance of combustible materials on the two sides of a forest fire isolation belt, and the flame-retardant material is high in flame retardance and good in long-term flame retardance and can effectively increase the content of nutrient elements in soil; the vegetation green-keeping time is effectively prolonged, the increase rate of the combustible loading capacity is reduced, the vegetation recovery efficiency after disasters is improved, the vegetation green recovery time of the second year is shortened, and therefore the probability of forest fire occurrence is reduced; a new way for resource utilization of the industrial solid waste is further expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of forest fire fighting and extinguishing, and in particular to a gypsum-based ecological flame retardant material for a mountain fire isolation zone and a preparation method thereof. Background Art

[0002] A forest fire is a multi-dimensional, multi-phase, multi-scale, unsteady, nonlinear, and non-equilibrium dynamic process in which matter, momentum, energy, and chemical components interact under complex and changing environmental conditions. Combustibles are the most critical factor in the fire triangle. Their characteristics essentially determine the severity of the consequences of a fire. At the same time, the type and distribution of combustibles determine the intensity and spread of forest fires. Dead branches and fallen leaves in forests are extremely flammable and are a major ignition source and risk hazard for forest fires. In order to reduce the combustible load in forests and reduce ignition sources, the isolation of combustibles is currently mainly achieved by establishing fire isolation belts. The construction of traditional isolation belts mainly involves manually clearing surface dead wood, weeds, shrubs and other combustibles and spraying flame retardant materials to form a covering layer on the combustibles to achieve the purpose of fire prevention and extinguishing. Existing forest fire prevention and extinguishing flame retardant materials include chemical agents, hydrogels, and foams. However, existing forest fire prevention and extinguishing flame retardant materials have the following defects and shortcomings:

[0003] 1. Chemical fire-fighting and flame-retardant materials such as ammonium phosphate, ammonium sulfate, borate and halogenated hydrocarbons generally have disadvantages such as low efficiency, strong corrosiveness, easy to decompose and deteriorate, difficult to degrade, and harmful to the human body.

[0004] 2. The moisture in hydrogel flame retardant materials will evaporate over time and lose their fire extinguishing effect, and long-term fire protection performance cannot be guaranteed.

[0005] 3. Water-based foams have higher production costs and require a large amount of foam to block combustion. In addition, the foam formed has a limited stabilization time, and the flame retardant properties will decrease as the foam ruptures.

[0006] 4. The existing flame retardant materials of isolation belts have poor compatibility with soil and plants, which can easily cause secondary pollution and affect the normal growth of plants. Summary of the Invention

[0007] The purpose of the present invention is to provide a gypsum-based ecological flame retardant material for mountain fire isolation belts and a preparation method thereof, so as to solve the problems of secondary pollution, poor long-term flame retardant performance, single functionality and high preparation cost of existing mountain fire isolation belt flame retardant materials.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solution: a gypsum-based ecological flame retardant material for mountain fire isolation belt, characterized in that the components included are as follows in parts by weight:

[0009]

[0010]

[0011] A further technical solution is that the building gypsum is prepared by calcining natural gypsum, purified phosphogypsum and desulfurized gypsum, and has a 2h flexural strength of ≥1MPa and a 2h compressive strength of ≥2MPa.

[0012] A further technical solution is that the flame retardant synergist is one or more of fly ash, silica fume, flotation tailings, and mineral powder, the fly ash grade is ≥ grade II, and grade I is better; the mineral powder grade is ≥ grade S75, and grade S95 is better.

[0013] A further technical solution is that the red soil comes from the construction forest area and is processed through a 25-mesh sieve.

[0014] A further technical solution is that the natural water-retaining mineral is one or more of diatomaceous earth, bentonite, and attapulgite; wherein the SiO2 content of diatomaceous earth is ≥75%, the pH is 6-8, and the suspension is ≥90%; the 2h water absorption rate of bentonite is ≥330%, the pH is 7-9; the specific surface area of attapulgite is 15-30m 2 / g.

[0015] A further technical solution is that the water-retaining agent is one or more of hydroxypropyl methylcellulose, carboxymethyl cellulose, dextrin, and starch ether, wherein the viscosity of hydroxypropyl methylcellulose and carboxymethyl cellulose is 5w-10w mPa·s.

[0016] A further technical solution is that the plant nutrient agent is one or more of sludge treated by anaerobic fermentation, animal manure treated by aerobic composting, humic acid, and fulvic acid, wherein the heavy metal content of the sludge after anaerobic fermentation is lower than the soil standard detection limit, and the Escherichia coli content of animal manure after aerobic composting meets the restriction standard for the use of organic fertilizer.

[0017] A further technical solution is that the microbial agent is one or more of a nitrogen-fixing bacteria agent, a phosphate-dissolving bacteria agent, a potassium-dissolving bacteria agent, and a Bacillus agent.

[0018] A further technical solution is that the retarder is one or more of sucrose, citric acid, tartaric acid, and sodium gluconate.

[0019] A further technical solution is that the preparation method of the gypsum-based ecological flame retardant material is as follows:

[0020] Add building gypsum, flame retardant synergist, red soil, natural water-retaining minerals, water-retaining agent, plant nutrient agent, microbial agent, retarder and water into a planetary mixer, stir at a stirring speed of 200-300 r / min for 5-10 minutes to obtain gypsum-based ecological flame retardant material slurry.

[0021] Flame Retardant Mechanism: 1. Condensed Phase Flame Retardant Mechanism: The micro-coagulation and particle adhesion of building gypsum powder enable gypsum-based ecological flame retardant materials to quickly adhere to combustible materials such as dead branches and leaves on the ground, forming a flame-retardant layer. This effectively isolates the combustible material from oxygen, interrupts the thermal decomposition reaction of the combustible material, and slows down the combustion process, thereby controlling the spread of the fire. 2. Vapor Phase Flame Retardant Mechanism: Under the combustion environment, the crystal water of calcium sulfate dihydrate in the gypsum ecological flame retardant material breaks free from its chemical bonds, releasing a large amount of non-combustible water vapor. This reduces the oxygen concentration around the combustible material, interrupting the combustion chain reaction and achieving a flame retardant effect. 3. Heat Exchange Interruption Flame Retardant Mechanism: Under high temperature, the calcium sulfate dihydrate in the gypsum ecological flame retardant material absorbs approximately 0.52-0.64 kJ / g of heat from the system during the dehydration reaction. This removes heat from the combustion environment, reducing heat accumulation, delaying and retarding the combustion process, and ultimately achieving a flame retardant effect. The fly ash, silica fume, diatomaceous earth, flotation tailings and mineral powder in gypsum ecological flame retardant materials contain a large amount of silicon dioxide, which can effectively combine with the carbon layer at high temperatures. The formed -Si-O-bonds and -Si-C-bonds can isolate oxygen and heat transfer, delay the thermal decomposition of the substrate, strengthen its solid phase flame retardant effect, and improve flame retardant properties.

[0022] The fly ash, silica fume, diatomaceous earth, flotation tailings, and mineral powder in this invention possess a large specific surface area and electrostatic adsorption capacity of the micropowder particles, enabling sufficient coverage of combustible materials by the gypsum ecological flame retardant material. The addition of fly ash acts as a flame retardant and smoke suppressant, effectively inhibiting smoke generation and enhancing its flame retardancy. Furthermore, fly ash prevents the dihydrate gypsum from agglomerating and compacting, improving the permeability of the gypsum ecological flame retardant material.

[0023] The building gypsum in gypsum-based ecological flame-retardant materials forms a porous structure after hydration to dihydrate gypsum. The numerous shell pores in diatomaceous earth, bentonite, and silica fume further enhance the air permeability of the flame-retardant layer. Combined with the inherent thermal insulation and moisture-retaining properties of dihydrate gypsum, this effectively maintains a suitable temperature, humidity, and ventilation for microorganisms in the soil. This enhances microbial activity, accelerates enzymatic reactions, and accelerates the decomposition of organic combustibles such as litter and leaves, creating humus. The resulting humus contains plant nutrients such as nitrogen, phosphorus, potassium, sulfur, and trace elements, which are slowly released through mineralization, continuously supplying vegetation growth. The humic acid, organic acids, and vitamins produced during humus decomposition stimulate plant growth and promote root development. Adequate plant nutrients effectively prolong the evergreenness of forest vegetation, thereby reducing the fuel load in the forest. Furthermore, the moisture in evergreen vegetation reduces its flammability, minimizing the risk of forest fires and the resulting damage from their spread.

[0024] The present invention adds anaerobic fermentation treated sludge, aerobic composted animal feces, humic acid and fulvic acid to the gypsum ecological flame retardant material, which has the following functional advantages: 1. Soil nutrient components: the organic matter, ammonium nitrogen and minerals contained in the anaerobic fermentation treated sludge and aerobic composted animal feces can promote the growth of forest vegetation; 2. Improve soil structure and physical properties: promote the formation of soil aggregates, increase soil porosity and aeration, provide a good physical environment for plant root growth, and improve soil water retention and cation exchange capacity. 1. Optimizes soil nutrient exchange capacity, reduces water and nutrient loss, and regulates soil pH, bringing the pH value within a suitable range for plant growth. 2. Improves nutrient utilization efficiency: Enhances complex formation with metal ions in the soil, increasing the availability of trace elements, promoting plant absorption and utilization, reducing the volatilization and leaching of phosphorus and nitrogen from the soil, and improving nutrient utilization. 3. Stimulates plant growth: Enhances stress tolerance by stimulating the growth and development of plant roots, increasing root length, root number, and root activity, and enhancing the root system's ability to absorb water and nutrients. This enhances plant resistance to drought, cold, disease, and pests, improving plant resilience and helping plants grow better in adverse environments. 4. Enhances soil microbial activity: Promotes the proliferation of beneficial soil microorganisms and improves the soil microbial community structure. Through these functional effects, the plant nutrient additives in gypsum ecological flame retardant materials achieve long-term greening of forest vegetation through improvements in soil physical and chemical properties, plant growth, stress tolerance, and microbial flora, while reducing the rate of increase in combustible material loads such as litter. At the same time, it improves the efficiency of forest vegetation growth and greening in the second year, shortens the greening time and the high-risk period of fire, and greatly reduces the possibility of wildfires in the second year.

[0025] The natural water-retaining minerals in the present invention have the characteristics of a large number of micropores and a large porosity, resulting in strong water absorption, good suspension performance, and light bulk density. They can achieve water retention in the gypsum ecological flame retardant material slurry and provide moisture for the growth and reproduction of microorganisms in vegetation and soil. The main chemical component of natural water-retaining minerals is silicon dioxide, which will not affect the original components of the soil. The water-retaining agent forms a cross-linked three-dimensional network structure in the gypsum ecological flame retardant material slurry. There are a large number of strong hydrophilic functional groups such as carboxyl and hydroxyl groups. After water molecules enter the network structure, they are hydrogen-bonded with these functional groups and are adsorbed and firmly retained in the network to achieve the water retention function of the flame retardant material. The retarder used in the present invention is a carboxylic acid and polysaccharide type retarder, which has obvious cost advantages compared with traditional protein retarders and greatly reduces the production cost of gypsum ecological flame retardant materials.

[0026] The addition of microbial agents to the present invention has the following effects: 1. It improves the aggregate structure of the gypsum ecological flame retardant material and soil, promoting the aggregation of small particles into larger aggregates, thereby enhancing the permeability and water and fertilizer retention capacity of the ecological flame retardant material. 2. It enhances soil enzyme activity by secreting enzymes, promoting the decomposition of organic combustibles and the formation of humic acid, thereby improving soil fertility. 3. It secretes antibiotics, active enzymes, and other substances to inhibit or kill pathogens in the soil, reducing the incidence of diseases and enhancing crop disease resistance. Among them, nitrogen-fixing bacteria can convert nitrogen in the air into ammonia that can be absorbed by plants, providing nitrogen nutrients necessary for plant growth; phosphate-dissolving bacteria and potassium-dissolving bacteria can convert insoluble phosphorus and potassium compounds in the soil into available phosphorus and available potassium that can be absorbed and utilized by plants, thereby improving the utilization rate of chemical fertilizers by increasing soil nutrient availability; and Bacillus agents improve plant physiological metabolic activities and enhance chlorophyll content, thereby increasing plant photosynthesis efficiency and promoting growth. They also produce a variety of antibiotics that effectively inhibit the growth and reproduction of various plant pathogenic fungi and bacteria. The microbial agent in the gypsum ecological flame-retardant material ensures vegetation growth and prolongs its green life through the aforementioned functional effects, reducing the combustible load and its rate of increase, thereby reducing the probability, frequency, and destructiveness of fires. The addition of red clay to the present invention not only slows the hydration and setting rate of building gypsum, but also preserves the original microbial community, preventing poor microbial adaptability and promoting normal microbial growth.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) Wildfire Isolation Zone Gypsum-Based Ecological Flame Retardant Materials utilize the low thermal conductivity and dehydration heat absorption of calcium sulfate dihydrate formed after the hydration of building gypsum. During a fire, the crystal water is quickly removed and absorbs heat from the system to reduce the fire temperature. At the same time, the water vapor generated isolates the air around the combustible material, achieving a highly effective flame retardant and suffocating effect. The crystal water in the calcium sulfate dihydrate structure is bound by chemical bonds and will not evaporate or be removed at natural temperatures, thus maintaining long-term flame retardant properties.

[0029] (2) By utilizing the micro-gelling properties of the gypsum-based ecological flame retardant material and the strong adsorption properties of the flame retardant synergist in the forest fire isolation zone, it can quickly adhere to combustible materials such as dead branches and fallen leaves and form a flame retardant layer, making the flame retardancy of combustible materials such as dead branches and fallen leaves reach a difficult-to-burn level, thereby reducing the load of combustible materials in the forest and effectively reducing the probability of forest fires. When a forest fire occurs, the flame retardant layer effectively isolates the air while preventing the combustion and decomposition of combustible materials, thereby controlling the expansion of the fire spread.

[0030] (3) The flame retardant layer formed by the gypsum-based ecological flame retardant material covering the wildfire isolation zone can accelerate the decomposition rate of organic combustibles on the surface by microorganisms in the soil. The plant nutrients and microbial agents in the flame retardant material can effectively increase the content of soil nutrients, thereby promoting the growth of forest vegetation, prolonging the greening time of vegetation, and at the same time improving the efficiency of vegetation regreening in the second year, shortening the regreening time, and reducing the probability of wildfires. It accelerates the efficiency of vegetation recovery after disasters, reduces the damage to the ecological environment caused by wildfires, and is conducive to the restoration and balance of the ecosystem.

[0031] (4) Compared with traditional fire extinguishing and flame retardant materials, the preparation and processing technology is simple, the cost advantage is significant, and the total smoke volume and the production of carbon monoxide and carbon dioxide gases can be reduced during the flame retardant process.

[0032] (5) The gypsum-based ecological flame retardant materials in wildfire isolation zones further expand new ways of resource utilization of industrial solid waste and realize a new green circular economy model of waste-based disaster reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the soil nutrient content comparison design in Example 1.

[0034] Figure 2 This is a schematic diagram of the flame retardant test stack design in Example 1.

[0035] Figure 3 This is a physical picture of the cross fire pile after burning for 1 minute in Example 1.

[0036] Figure 4 This is a physical picture of the cross fire pile after burning for 3 minutes in Example 1. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0038] Example 1

[0039] This embodiment provides a gypsum-based ecological flame-retardant material for a wildfire isolation zone and a preparation method thereof. The specific steps are as follows:

[0040] (1) The building gypsum prepared by calcining desulfurized gypsum has a 2h flexural strength and a 2h compressive strength of 2.5MPa and 5.8MPa respectively.

[0041] (2) The following raw materials were weighed in parts by weight: 520 parts of building gypsum, 60 parts of fly ash (grade I), 50 parts of flotation tailings, 15 parts of silica fume, 45 parts of mineral powder (grade S95), 170 parts of red clay, 20 parts of diatomaceous earth (SiO2 content of 80%, pH of 6.8, suspension of 93%), 27 parts of bentonite (water absorption rate of 350% in 2h, pH of 8.1), 25 parts of attapulgite (specific surface area of 25.4m 2 / g), 8 parts of sewage sludge treated by anaerobic fermentation, 55 parts of animal feces treated by aerobic composting, 30 parts of humic acid, 0.08 parts of nitrogen-fixing bacteria agent, 0.05 parts of phosphate-dissolving bacteria agent, 0.05 parts of potassium-dissolving bacteria agent, 0.03 parts of Bacillus agent, 1 part of hydroxypropyl methylcellulose (viscosity of 7 WmPa·s), 0.75 parts of starch ether, 2 parts of sucrose, and 1.25 parts of sodium gluconate.

[0042] (3) The above-mentioned materials in parts by weight were mixed with 600 parts of water in a planetary mixer at a stirring speed of 220 r / min for 5 minutes to prepare a gypsum-based ecological flame retardant material slurry for the wildfire isolation zone, which was then covered on the combustible surfaces on both sides of the wildfire isolation zone by spraying.

[0043] (4) Intact pine wood that had been naturally dried was used as the experimental combustible. A blank group and a control group were set up. The blank group consisted of untreated combustibles, and the experimental group consisted of combustibles that had been uniformly coated with the gypsum-based ecological flame retardant material slurry and then air-dried. The flame retardant properties of the gypsum-based ecological flame retardant material were determined by measuring the limiting oxygen index, cone calorimetry data, and smoke release of the combustibles in the experimental and blank groups. The comparison of the test results is shown in Table 1.

[0044] Table 1 Flame retardant performance test results

[0045] Sample processing method Unprocessed Coated gypsum-based ecological flame retardant material Limiting oxygen index (%) 22.4 35 Initial ignition time (s) 4 20 <![CDATA[Heat release rate (kW / m 2 )]]> 187.236 51.458 <![CDATA[Total heat release (MJ / m 2 )]]> 42.2125 14.2367 Effective heat of combustion (MJ / kg) 48.565 13.985 CO production rate (kg / kg) 0.2456 1.3587 CO2 production rate (kg / kg) 5.4325 4.7562 <![CDATA[Total smoke release amount (m 2 / m 2 )]]> 135.5864 102.3254

[0046] The limiting oxygen index (LOI) is an indicator of how easily a material burns when exposed to flame in air. Since there is currently no specific LOI evaluation standard for wood, the national LOI standard for plastics is generally used to evaluate wood. According to national standard GB2406-1993, a material with an LOI of <21% is considered flammable, a material with an LOI between 22% and 26% is self-extinguishing, and a material with an LOI >27% is considered flame-retardant. Table 1 shows that the untreated combustible material is flammable, but after coating with the gypsum-based ecological flame-retardant material, the material reaches a flame-retardant level, demonstrating the material's excellent flame retardancy. The ignition time refers to the duration of sustained ignition required for flames to form on the wood surface. A longer ignition time indicates a material's less ignitability and better flame retardancy. In Table 1, coating the combustible with the gypsum-based ecological flame-retardant material extends the ignition time from 4 seconds to 20 seconds. This is because the flame-retardant layer on the combustible surface effectively isolates the combustible from oxygen after contact with the fire source, interrupting the thermal decomposition reaction. Simultaneously, the calcium sulfate dihydrate absorbs heat and forms water vapor during the removal of water of crystallization, reducing the oxygen concentration around the combustible, thereby interrupting the combustion chain reaction. This significantly improves the combustible's flame retardancy and prolongs the ignition time. The heat release rate and total heat release values represent the material's thermal decomposition rate. The greater the heat released during combustion, the more combustible volatile substances are generated, the easier the material burns, and the greater the fire hazard. The effective heat of combustion refers to the heat released by the combustion of combustible gases released by the decomposition of the material. A higher effective heat of combustion indicates a higher level of combustible gases generated during combustion. After the combustibles were coated with gypsum-based ecological flame retardant materials, the heat release rate, total heat release value and effective combustion heat were significantly reduced, indicating that the gypsum-based ecological flame retardant materials effectively prevented the release of heat from the combustibles and reduced the combustion heat release. The total smoke release reflects the total amount of smoke released during combustion and is an important flame retardant performance parameter for evaluating the fire safety of materials. Among them, incomplete combustion of combustibles will produce toxic carbon monoxide gas, and carbon dioxide will be released synchronously with the combustion heat. The production of carbon monoxide and carbon dioxide is an important criterion for evaluating the performance of flame retardant materials. Table 1 shows that coating with gypsum-based ecological flame retardant materials can effectively inhibit the generation of combustible smoke and reduce the yield of toxic carbon monoxide gas and greenhouse gas carbon dioxide. This further illustrates the green and environmentally friendly nature of gypsum-based ecological flame retardant materials.

[0047] (5) Soil nutrient content test

[0048] A blank group and a control group were set up. The blank group was soil covered with dead branches and leaves, and the experimental group was soil covered with dead branches and leaves after spraying gypsum-based ecological flame retardant materials. Figure 1As shown. Thirty days after spraying the gypsum-based ecological flame retardant material, soil samples were collected from the 15-20 cm depth of the blank and control groups. After removing foreign matter, the soil samples were air-dried and then passed through a 2 mm sieve. The sieved material was aliquoted into three portions for testing. Soil nutrient content was determined as follows: soil organic matter content was determined using the potassium dichromate volumetric method with oil bath heating; total nitrogen content was determined using the semi-micro Kjeldahl method; total phosphorus content was determined using the sodium hydroxide alkali fusion-molybdenum antimony colorimetric method; total potassium content was determined using acid dissolution-flame photometry; available phosphorus content was determined using the sodium bicarbonate extraction-molybdenum antimony colorimetric method; and available potassium content was determined using ammonium acetate extraction-flame photometry.

[0049] Through the comparative analysis of the soil nutrient content test results in Table 2, it can be seen that the nutrient content in the soil under the combustible material after spraying the gypsum-based ecological flame retardant material is significantly higher than that in the blank group, indicating that the gypsum-based ecological flame retardant material can effectively improve soil fertility. The increase in soil fertility helps to prolong the greening time of vegetation and reduce the rate of increase in combustible load, thereby reducing the probability of wildfires. At the same time, sufficient nutrient content in the soil can accelerate the efficiency of vegetation recovery after the disaster and shorten the time for vegetation to regreen in the second year.

[0050] Table 2 Soil nutrient content

[0051] Soil source Unprocessed Coated gypsum-based ecological flame retardant material Organic matter (g / kg) 25.46 29.63 Total nitrogen (g / kg) 1.23 1.85 Total phosphorus (g / kg) 0.42 0.83 Total potassium (mg / kg) 18.66 24.12 Available phosphorus (mg / kg) 6.31 9.36 Fast-acting potassium (mg / kg) 38.65 47.36

[0052] (6) Field combustion simulation experiment

[0053] 6.1 Flame retardant experimental design

[0054] Use rice straw to build a cross pile on the open cement ground, and then pre-treat the vertical part of the pile by blanking, spraying gypsum-based ecological flame retardant materials, and spraying water, and then leave it for 24 hours. Figure 2 As shown in the figure, the flame retardant properties of the flame retardant material are determined by igniting the rice stalks from the ignition source on the left and observing the burning conditions of the pile.

[0055] 6.2 Combustion conditions

[0056] Depend on Figure 3 It can be seen that after burning for 1 minute, the untreated fire pile burned violently and the fire spread quickly; the fire pile sprayed with gypsum-based ecological flame retardant material burned to the center and stopped burning; the fire pile sprayed with water burned less fiercely, spread slowly and was accompanied by a large amount of white smoke. Figure 4 It can be seen that both the untreated and water-sprayed cross fires were able to burn completely, while the fire sprayed with gypsum-based ecological flame retardant material was extinguished at the center. This shows that gypsum-based ecological flame retardant material has good flame retardant properties and its long-term flame retardant effect is better than water.

[0057] Example 2

[0058] This embodiment provides a gypsum-based ecological flame-retardant material for a wildfire isolation zone and a preparation method thereof. The specific steps are as follows:

[0059] (1) The building gypsum prepared by calcining purified phosphogypsum has a 2h flexural strength and a 2h compressive strength of 2.0 MPa and 4.1 MPa, respectively.

[0060] (2) The following raw materials were weighed in parts by weight: 600 parts of building gypsum, 50 parts of fly ash (grade I), 40 parts of flotation tailings, 10 parts of silica fume, 35 parts of mineral powder (grade S95), 160 parts of red clay, 15 parts of diatomaceous earth (SiO2 content of 85%, pH of 6.5, suspension of 94%), 25 parts of bentonite (2h water absorption rate of 345%, pH of 7.7), 40 parts of sludge treated by anaerobic fermentation, 25 parts of animal manure treated by aerobic composting, 0.25 parts of fulvic acid, 0.04 parts of nitrogen-fixing bacteria agent, 0.06 parts of phosphate-dissolving bacteria agent, 0.03 parts of potassium-dissolving bacteria agent, 0.03 parts of Bacillus agent, 1.25 parts of hydroxypropyl methylcellulose (viscosity of 5 WmPa·s), 0.5 parts of starch ether, 1.5 parts of sucrose, and 0.75 parts of sodium gluconate.

[0061] (3) The above-mentioned materials in parts by weight were mixed with 550 parts of water in a planetary mixer at a stirring speed of 250 r / min for 7 minutes to prepare a gypsum-based ecological flame retardant material slurry for the wildfire isolation zone, which was then covered on the combustible surfaces on both sides of the wildfire isolation zone by spraying.

[0062] (4) Smooth, intact pine wood that had been naturally dried was used as the combustible. A blank group and a control group were set up. The blank group consisted of untreated combustibles, while the experimental group consisted of combustibles that had been evenly coated with the gypsum-based ecological flame retardant material slurry and then air-dried. The flame retardant properties of the gypsum-based ecological flame retardant material were determined by the limiting oxygen index, cone calorimetry data, and smoke emission test results of the experimental and blank groups. The test results are shown in Table 3.

[0063] The comparative analysis of the flame retardant performance indicators of combustible materials before and after application of the gypsum-based ecological flame retardant material in Table 3 demonstrates that the gypsum-based ecological flame retardant material can transform combustible materials from highly flammable to difficult to burn, prolong the initial ignition time, reduce the total heat release and heat release rate, and simultaneously reduce the total smoke emission and the production of carbon monoxide and carbon dioxide. This demonstrates that the gypsum-based ecological flame retardant material possesses excellent flame retardant properties. A comparison with Example 1 demonstrates that increasing the proportion of building gypsum in the gypsum-based ecological flame retardant material can improve the flame retardant properties of combustible materials to a certain extent.

[0064] Table 3 Flame retardant performance test results

[0065] Sample processing method Unprocessed Coated gypsum-based ecological flame retardant material Limiting oxygen index (%) 22.4 37 Initial ignition time (s) 4 24 <![CDATA[Heat release rate (kW / m 2 )]]> 187.236 48.692 <![CDATA[Total heat release (MJ / m 2 )]]> 42.2125 13.7691 Effective heat of combustion (MJ / kg) 48.565 13.325 CO production rate (kg / kg) 0.2456 1.3157 CO2 production rate (kg / kg) 5.4325 4.6548 <![CDATA[Total smoke release amount (m 2 / m 2 )]]> 135.5864 97.5687

[0066] (5) Soil nutrient content test

[0067] The differences in nutrient content in the soil beneath fallen branches and leaves after spraying with gypsum-based ecological flame retardant materials (Table 4) compared to untreated soil demonstrate that gypsum-based ecological flame retardant materials significantly increase soil nutrient content, helping to prolong vegetation greening, reduce the probability of wildfires, mitigate the risk of forest fires and the damage caused by their spread, and accelerate post-disaster vegetation recovery. Compared with Example 1, increasing the ratio of anaerobic fermentation-treated sludge to aerobic composted animal manure in the gypsum-based ecological flame retardant materials further improves soil nutrient content.

[0068] Table 4 Soil nutrient content

[0069] Soil source Untreated soil Soil coated with gypsum-based ecological flame retardant material Organic matter (g / kg) 25.46 27.83 Total nitrogen (g / kg) 1.23 1.71 Total phosphorus (g / kg) 0.42 0.68 Total potassium (mg / kg) 18.66 22.42 Available phosphorus (mg / kg) 6.31 8.14 Fast-acting potassium (mg / kg) 38.65 44.66

[0070] The basic principles, main features, and advantages of the present invention are shown and described above. It should be understood by those skilled in the art that the present invention is not limited to the above-described embodiments. The above-described embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention claimed.

Claims

1. A gypsum-based ecological flame retardant material for mountain fire isolation belts, characterized by: The components included are as follows by weight:

2. The gypsum-based ecological flame-retardant material for mountain fire isolation zones according to claim 1, characterized in that: The building gypsum is prepared by calcining natural gypsum, purified phosphogypsum and desulfurized gypsum, and has a 2h flexural strength of ≥1MPa and a 2h compressive strength of ≥2MPa.

3. The gypsum-based ecological flame-retardant material for mountain fire isolation zones according to claim 1, characterized in that: The flame retardant synergist is one or more of fly ash, silica fume, flotation tailings, and mineral powder. The fly ash grade is ≥ grade II, and the mineral powder grade is ≥ grade S75.

4. The gypsum-based ecological flame-retardant material for mountain fire isolation zones according to claim 1, characterized in that: The red soil was processed through a 25-mesh sieve.

5. The gypsum-based ecological flame-retardant material for mountain fire isolation zones according to claim 1, characterized in that: The natural water-retaining mineral is one or more of diatomaceous earth, bentonite, and attapulgite; wherein the SiO2 content of diatomaceous earth is ≥75%, the pH is 6-8, and the suspension is ≥90%; the 2h water absorption rate of bentonite is ≥330%, the pH is 7-9; the specific surface area of attapulgite is 15-30m 2 / g.

6. The gypsum-based ecological flame-retardant material for mountain fire isolation zones according to claim 1, characterized in that: The water-retaining agent is one or more of hydroxypropyl methylcellulose, carboxymethyl cellulose, dextrin, and starch ether, wherein the viscosity of hydroxypropyl methylcellulose and carboxymethyl cellulose is 5w-10w mPa·s.

7. The gypsum-based ecological flame-retardant material for mountain fire isolation zones according to claim 1, characterized in that: The plant nutrient is one or more of sludge treated by anaerobic fermentation, animal feces treated by aerobic composting, humic acid, and fulvic acid, wherein the heavy metal content of the sludge after anaerobic fermentation is lower than the soil standard detection limit, and the Escherichia coli content of the animal feces after aerobic composting meets the restriction standard for the use of organic fertilizer.

8. The gypsum-based ecological flame-retardant material for mountain fire isolation zones according to claim 1, characterized in that: The microbial agent is one or more of a nitrogen-fixing agent, a phosphate-dissolving agent, a potassium-dissolving agent, and a Bacillus agent.

9. The gypsum-based ecological flame-retardant material for mountain fire isolation zones according to claim 1, characterized in that: The retarder is one or more of sucrose, citric acid, tartaric acid and sodium gluconate.

10. The gypsum-based ecological flame-retardant material for mountain fire isolation zones according to any one of claims 1 to 9, characterized in that: The preparation method of the gypsum-based ecological flame retardant material is as follows: Add building gypsum, flame retardant synergist, red soil, natural water-retaining minerals, water-retaining agent, plant nutrient agent, microbial agent, retarder and water into a planetary mixer, stir at a stirring speed of 200-300 r / min for 5-10 minutes to obtain gypsum-based ecological flame retardant material slurry.

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