Water-avoiding hazardous chemical fire fighting sand and its manufacturing method

Abstract

This invention pertains to fire-fighting and rescue industry supplies and their manufacturing methods, specifically relating to fire-fighting sand for water-repellent hazardous chemical fires and its manufacturing method. It utilizes the characteristic of expanded perlite particles forming a honeycomb-like porous structure after high-temperature expansion, and its ability to absorb liquids, to produce fire-fighting sand for fire suppression. Taking advantage of the liquid absorption properties of expanded perlite particles, the particles are soaked in a saturated solution of extinguishing agent, stirred evenly, fully saturated, drained, and then dried at low temperature. This process of soaking, stirring, fully saturating, draining, and low-temperature drying is repeated multiple times. The expanded perlite particles impregnated with extinguishing agent form fire-fighting sand, the bulk density of which is lower than the specific gravity of the water-repellent hazardous liquid. It fully utilizes the excellent fire-extinguishing properties of carbon dioxide to extinguish combustibles. It generates a large amount of water vapor, forming an air curtain that both lowers the fire temperature and effectively isolates oxygen, thus slowing the temperature rise of metal containers and stored liquids.

Description

Technical Field

[0001] This invention pertains to fire-fighting and rescue industry supplies and their manufacturing methods, and specifically relates to a fire-fighting sand for water-repellent hazardous chemical fires and its manufacturing method. Background Technology

[0002] Fires in water-sensitive liquid hazardous chemical storage tanks are extremely dangerous. If firefighting is not timely, or if inappropriate extinguishing agents or methods are used, explosions, boiling over, splashing, high-temperature rupture of the tank, and flowing fires often occur, causing casualties among firefighters, damage to equipment and property, and environmental pollution. In the case of boiling over oil storage tank fires, there are few means to control, delay, or avoid the time and danger of boiling over and splashing. For fires involving polar liquid hazardous chemicals such as ketones, alcohols, esters, ethers, aldehydes, and amines, these substances are natural defoamers, and various types of fire-fighting foams cannot form an effective coverage on the liquid surface. In storage tank fires, the tank walls are extremely prone to failure, rupture, and collapse at high temperatures, forming large-scale flowing fires, and there are few means to protect and maintain the effectiveness of the tank walls during a fire. Fires and explosions in large chemical enterprises and concentrated tank areas can trigger chain reactions and produce catastrophic consequences.

[0003] Ordinary fire sand, normally stored in fire sand boxes (pools), can only be manually scattered to cover the fire source, with limited effectiveness and being extremely close to the danger. Ordinary fire sand and dry powder extinguishing agents have a specific gravity between 1.47 and 2.9. When used to extinguish liquid fires, the fire sand and dry powder extinguishing agent will quickly settle to the bottom of the liquid, not only failing to extinguish the fire but also increasing the liquid level, increasing the risk of liquid overflowing from the storage tank and forming a flowing fire.

[0004] The combustion characteristics of pool fires vary greatly. A 7.1cm diameter oil pan pool fire exhibits laminar combustion, a 30cm diameter oil pan pool fire is in a transitional stage of combustion, while an oil pan pool fire with a diameter of 100cm or more exhibits fully turbulent combustion. As the diameter of the oil pan and the combustion area increase, the heat radiation flux density, intensity, flame height, and susceptibility increase geometrically in a direct proportional manner. Firstly, the presence of a water cushion layer or water accumulation layer within the tank can cause heat waves to be conducted downwards layer by layer to the bottom water cushion layer due to the prolonged combustion of wide-boiling-range oil. This heat reaches and exceeds the boiling point of water, causing a large amount of supersaturated vapor to accumulate and generate high pressure. This pressure breaks through the weight of the upper oil layer, carrying it upwards in a jet or explosion, resulting in splashing. Secondly, the collapse of a large amount of fire-fighting foam (3% or 6%) due to heat releases a large amount of water. Some of this water evaporates, while some sinks to the bottom of the tank, reaching the water cushion layer and raising the liquid level. The larger the amount of fire-fighting cooling water and foam sprayed, the more water sinks into the tank, increasing the likelihood of overheating, boiling over, and splashing. The high temperature and heat generated by the combustion of liquid inside the storage tank rapidly evaporate, destroy, and damage the fire-fighting foam, making it impossible for the fire-fighting foam to achieve a long-lasting and effective coverage.

[0005] Large oil tank fires require the use of large-scale carbon dioxide extinguishing. However, carbon dioxide extinguishers are typically small containers, and large carbon dioxide tank trucks pose significant safety hazards during storage, transportation, and use, and are themselves major hazard sources. There are currently no large carbon dioxide gas fire trucks in the domestic or international fire fighting and rescue field. The spray distance of carbon dioxide gas is only about 5-9 meters, while large storage tanks often have a diameter of around 100 meters and a height of up to 20 meters. This distance prevents the gas from reaching the center of the fire, hindering rapid and effective firefighting. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a lightweight, floatable fire-fighting sand for water-repellent hazardous chemical fires, capable of floating and covering the liquid surface inside the tank, capable of long-distance spraying, releasing carbon dioxide and water vapor when exposed to high temperatures, and having good fire-extinguishing performance, as well as a method for its preparation.

[0007] The technical solution adopted by the present invention to solve the technical problem is: the carrier of the fire-fighting sand used for fires in water-sensitive liquid hazardous chemical storage tanks is expanded perlite, and the extinguishing material is sodium bicarbonate or potassium bicarbonate.

[0008] Expanded perlite: It is made by crushing perlite ore and then expanding it at a high temperature of 1000-1380 degrees Celsius. The bulk density of expanded perlite is 80-150 kg / m³. 3 It absorbs 2-3.5 times its own weight in water.

[0009] Expanded perlite is a white, granular inorganic material with a honeycomb structure, produced by preheating and rapidly heating perlite ore to expand it. The principle is as follows: perlite ore is crushed into sand of a certain particle size, preheated, and then rapidly heated (above 1000℃). The moisture in the sand vaporizes and expands within the softened, glassy sand, forming a porous structure and expanding in volume 10-30 times. This invention utilizes the honeycomb-like porous structure formed inside perlite after high-temperature expansion and its ability to absorb liquids to create fire-fighting sand.

[0010] Sodium bicarbonate: with the molecular formula NaHCO3, is an inorganic compound, appearing as a white crystalline powder. It is odorless, has a salty taste, and is readily soluble in water. It slowly decomposes in humid or hot air at temperatures exceeding 60 degrees Celsius, producing carbon dioxide. It completely decomposes when heated to 270 degrees Celsius. It can be used in the production of acid-base fire extinguishers and foam fire extinguishers.

[0011] Potassium bicarbonate: with the molecular formula KHCO3, is an inorganic salt, a colorless and transparent monoclinic crystal or a white crystal; odorless, salty in taste, easily soluble in water, and its aqueous solution is weakly alkaline; potassium bicarbonate is stable in air, but decomposes when heated to 100-120℃, and completely decomposes at 200℃, losing carbon dioxide and water to form potassium carbonate, which can be used as a fire extinguishing agent for petroleum and chemicals.

[0012] Sodium bicarbonate and potassium bicarbonate are both ionic compounds that exist in solution in an ionic state. Their ionic diameter (or length) is 10 to the power of -10 meters, which is much smaller than that of nanoparticles (nanoparticles have a length of 10 to the power of -9 meters). They have a larger specific surface area and can therefore be called ultra-nanoparticles.

[0013] The method for preparing fire-fighting sand for water-repellent liquid hazardous chemical storage tanks using the above three raw materials is as follows: Step 1: Take several kilograms of expanded perlite, immerse the prepared expanded perlite granules in a saturated sodium bicarbonate solution at 60-80℃, and stir evenly. After the expanded perlite granules are fully saturated, drain them and dry them at low temperature. The weight of the expanded perlite granules after the first immersion and drying is increased by 72.7%. Step 2: Immerse the expanded perlite granules, which have increased in weight after drying, in a saturated sodium bicarbonate solution at 60-80℃ for the second time, stir evenly, drain them after full saturation, and dry them at low temperature. The weight of the expanded perlite granules after the second immersion and drying is increased by 145.4% compared to their initial weight. Step 3: immerse the expanded perlite granules, which have been dried at low temperature for the second time, in a saturated sodium bicarbonate solution at 60-80℃ for the third time. The expanded perlite particles are immersed in a saturated sodium bicarbonate solution at 60-80℃ and stirred until fully saturated. After immersion, they are drained and dried at low temperature. The expanded perlite particles after the third drying increase in weight by 218.1% compared to their initial weight. In the fourth step, the expanded perlite particles after the third drying are immersed in a saturated sodium bicarbonate solution at 60-80℃ for the fourth time. After immersion, they are drained and dried at low temperature. The expanded perlite particles after the fourth drying increase in weight by 290.9% compared to their initial weight. The number of times the expanded perlite particles are immersed in the saturated sodium bicarbonate solution depends on the bulk density of the expanded perlite particles after low-temperature drying and whether the carbon dioxide and water vapor released by the complete decomposition of the sodium bicarbonate at 270℃ can achieve the fire extinguishing function. Expanded perlite was impregnated with a saturated potassium bicarbonate solution. Several kilograms of expanded perlite and potassium bicarbonate solution were used. Step one: the expanded perlite particles were immersed in the saturated potassium bicarbonate solution at 60-80℃ and stirred evenly. After the expanded perlite particles were fully saturated, they were drained and dried at a low temperature. After low-temperature drying, the expanded perlite particles increased in weight by 272.7% compared to their initial weight. Step two: the expanded perlite particles, after the first low-temperature drying, were second-impregnated in the saturated potassium bicarbonate solution at 60-80℃, stirred evenly, fully saturated, drained, and dried at a low temperature. After the second low-temperature drying, the expanded perlite particles increased in weight by 545.4% compared to their initial weight. The number of times the expanded perlite particles were impregnated in the saturated potassium bicarbonate solution was determined based on the bulk density of the expanded perlite particles after low-temperature drying and whether the carbon dioxide and water vapor released by the complete decomposition of the potassium bicarbonate at 200℃ achieved a fire extinguishing function.

[0014] Expanded perlite particles, after being impregnated with a saturated solution of potassium bicarbonate or sodium bicarbonate and dried, have a bulk density lower than that of various heavy oil products, fuel oils, and wide-boiling-range boiling overflow oil products. This allows the expanded perlite, which is also known as fire-fighting sand, impregnated with sodium bicarbonate or potassium bicarbonate extinguishing agents, to float on the surface of burning heavy oil products during the fire-fighting process. Under the high temperature of oil combustion, the sodium bicarbonate or potassium bicarbonate in the fire-fighting sand decomposes and releases carbon dioxide and water vapor, which can extinguish the fire.

[0015] The beneficial effects of this invention are as follows: Firefighting sand for water-sensitive hazardous chemical fires and its manufacturing method are produced in a saturated solution of sodium bicarbonate or potassium bicarbonate. Both substances are ionic compounds, existing in an ionic state in solution. Under the manufacturing method of this invention, the sodium bicarbonate or potassium bicarbonate extinguishing agent can deeply impregnate the honeycomb-like structure of perlite with its ultra-large specific surface area after high-temperature expansion. The expanded perlite particles containing ultra-nano-sized sodium bicarbonate or potassium bicarbonate possess powerful fire extinguishing capabilities, which is what this invention refers to as firefighting sand. The produced firefighting sand particles have a specific gravity of less than 0.7 tons / cubic meter, but still have a certain weight, allowing for long-distance spraying of the firefighting sand to the combustion site using professional fire spraying equipment. It forms a continuous, relatively stable, heat-insulating soft floating layer on the surface of various heavy oil products and wide-boiling-range oil products, floating and covering the burning liquid surface, forming a stable heat-insulating layer. The four conditions for combustion to occur and develop are combustible material, oxidizer, ignition source, and chain reaction free radicals. When fire-fighting sand is sprayed above burning oil, because it is lighter than the combustible material, it floats on top of the combustible material, forming a floating layer of granular sand. This prevents the combustible material from reacting with the oxidizer, i.e., oxygen. The fire-fighting sand layer also acts as insulation, limiting and eliminating the conditions for the formation of chain reaction free radicals during combustion, thus playing a role in extinguishing the fire. When the fire-fighting sand layer encounters the high temperatures of the fire scene, the extinguishing agents such as potassium bicarbonate or sodium bicarbonate, which are repeatedly impregnated in the pores of the honeycomb structure of the fire-fighting sand, undergo a high-temperature chemical reaction, releasing a large amount of carbon dioxide and water vapor. This fully utilizes the excellent extinguishing properties of carbon dioxide to extinguish the combustible material. The large amount of water vapor produced forms an air curtain, which not only lowers the temperature of the fire scene but also effectively isolates oxygen. A fire-fighting sand floating layer of a certain insulation thickness occupies the gas-phase combustion space inside the tank above the burning liquid surface, preventing direct heat radiation from the liquid combustion onto the dry wall of the storage tank and slowing down the rate of temperature rise of the metal tank and the stored liquid. The dry wall of the storage tank refers to the part of the tank wall above the liquid surface that is in contact with the air and does not come into contact with the liquid. Therefore, it can effectively block, weaken, or even eliminate dangerous situations such as explosions, boiling over, splashing, high-temperature rupture of the storage tank, and flowing fires. Fire-fighting sand impregnated with extinguishing agents has a lower specific gravity than various types of polar flammable liquids, allowing it to float and cover the surface of the flammable liquid. This provides a solid foothold for various types of foam, enabling foam or alcohol-resistant foam extinguishing agents to form and spread on a soft floating layer (bed) of fire-fighting sand of a certain thickness. This alters the formation and spreading conditions of the foam extinguishing agent, preventing direct contact between various types of extinguishing foam and the surface of the flammable polar liquid, protecting the stability, effectiveness, and durability of the foam layer coverage. It also avoids the inconvenience and dangers of transporting carbon dioxide, fully utilizes the fire extinguishing properties of carbon dioxide, and is particularly effective for fires in heavy oil storage tanks where large quantities of carbon dioxide are needed for fire suppression. The fire-fighting sand produced by this invention is in solid form, making it convenient and safe to transport. Storage conditions and costs are low, and it can meet storage requirements under normal temperature and dry conditions.

[0016] The following is a detailed description with reference to specific examples. Detailed Implementation

[0017] Example 1: Expanded perlite is produced by crushing perlite ore and then expanding the ore sand through high-temperature (1000-1380 degrees Celsius). There are two types of finished expanded perlite: open-crust perlite and closed-crust perlite (also known as vitrified microspheres). The production principle and method of perlite fire-fighting sand: Expanded perlite has a bulk density of 80-150 kg / m³ and absorbs 2-3.5 times its own weight in water. Utilizing the water absorption property of expanded perlite, it is soaked in a saturated solution of the main extinguishing agent (such as potassium bicarbonate and sodium bicarbonate) in a dry powder fire extinguishing agent. After uniform stirring until saturated, it is drained and then dried at a low temperature.

[0018] The table below shows the solubility of sodium bicarbonate and potassium bicarbonate at different temperatures. The density of sodium bicarbonate is 2.159 g / cm3, and the density of potassium bicarbonate is 2.17 g / cm3.

[0019] Temperature (°C) 50 60 70 80 Density (g / cm3) Solubility of sodium bicarbonate (%) 14.45 16.4 18.5 21.1 2.159 Potassium bicarbonate solubility (%) 54.5 65.6 74.5 83.8 2.17

[0020] The moisture in the expanded perlite granules impregnated with extinguishing agents is evaporated during the drying process, and the effective extinguishing agent is impregnated in the honeycomb structure of the expanded perlite granules in the form of ultra-nano-sized particles. Through repeated soaking, stirring, saturated leaching, and low-temperature drying, the dosage of extinguishing agent impregnated in the expanded perlite granules continuously increases, and the specific gravity of the expanded perlite continuously increases. Ultimately, the extinguishing agent completely impregnates and coats the expanded perlite layer by layer. However, the overall specific gravity of the final expanded perlite granular sand must be controlled to be less than 0.7 tons / cubic meter. This ensures that the fire-fighting sand carrying the extinguishing agent can float on the surface of various types of heavy oil or wide-boiling-range oil products.

[0021] The specific gravity of various heavy oil products, fuel oils, and wide-boiling-range boiling-over oil products is greater than 0.7 tons / cubic meter. For example, the specific gravity of crude oil is between 0.75 and 0.95 tons / cubic meter; less than 0.9 is light crude oil, and greater than 0.9 is heavy crude oil. The specific gravity of diluted asphalt is around 0.95-0.98; the specific gravity of heavy oil is generally between 0.82 and 0.95; and the specific gravity of fuel oil is generally between 0.8 and 0.98. Based on the principle of specific gravity and buoyancy, expanded perlite particles carrying fire extinguishing agents can form a continuous and relatively stable insulating soft floating layer (bed) on the surface of various heavy oil products and wide-boiling-range oil products. This solid particle floating layer floats and covers the liquid surface and has a certain insulating thickness. Due to the wall effect, where particles easily adhere to and accumulate near the tank wall, fire-fighting sand tends to accumulate near the tank wall, effectively isolating, isolating, preventing, and reducing direct heating of the tank wall by the combustion flame and heat radiation to the flammable liquid inside. The thicker the fire-fighting sand layer, the better the insulation effect and the greater the buoyancy, preventing the liquid inside the tank from heating up rapidly. The large volume of fire-fighting sand particles raises the liquid level inside the tank, crowding out, reducing, and filling the gas-phase combustion space. This effectively dissipates the heat generated by combustion outside the tank, releasing the flame and heat to the outside and upper space of the tank. It protects the previously exposed dry wall area above the liquid level from direct heating, thus maintaining the tank's load-bearing capacity. The extinguishing agent impregnated in expanded perlite particles reacts at high temperatures, releasing large amounts of carbon dioxide and water vapor inside the tank. According to calculations and experiments, 1000g of sodium bicarbonate completely decomposes at 270 degrees Celsius, releasing 145.8L of carbon dioxide and 125.5L of water vapor. 1000g of potassium bicarbonate completely decomposes at 200°C, releasing 122.5L of carbon dioxide and 115L of water vapor (calculated values ​​are basically consistent with experimental results). The generated carbon dioxide gas deposits and accumulates above the liquid surface and at the bottom of the gas phase combustion space inside the tank, inhibiting flame combustion; the generated water vapor lowers the temperature of the combustion zone and forms an air curtain above the burning liquid surface, isolating air and playing a gas extinguishing role in large tank liquid fires. A layer of fire-fighting sand particles of a certain thickness is formed on the liquid surface inside the tank. The gaps and pores between the sand particles are small and dense, which conforms to the structural principle of the flame arrester core layer. This allows the huge flame to be divided and compressed into several small flame streams after passing through the floating, dense fire-fighting sand layer, reducing the intensity and severity of combustion. This reduces heat radiation, heat convection, and heat conduction to the liquid and tank walls inside the tank. The combustion rate of heavy oil products in the tank and the temperature of the heat wave formed into the deeper liquid are greatly reduced. This reduces, delays, and avoids the time and danger of boiling over and splashing in the burning tank. This provided firefighters with the time and opportunity to calmly employ various firefighting methods, including foam extinguishing. It also ensured the safety of the storage tank, firefighters, and firefighting equipment.

[0022] Expanded perlite has a particularly strong adsorption capacity. In one case, a school gymnasium collapsed because a large amount of expanded perlite granules were piled on its roof during construction. After rain, the perlite absorbed water, increasing its weight several times over. This invention also utilizes the liquid adsorption property of expanded perlite. Soaking it in a saturated solution of sodium bicarbonate or potassium bicarbonate increases its weight several times, allowing it to adsorb a large amount of effective fire extinguishing agents.

[0023] This invention is not limited to attaching or encapsulating expanded perlite particles with sodium bicarbonate or potassium bicarbonate fire extinguishing agents. After being expanded at high temperatures, the expanded perlite particles form a honeycomb structure. Through a specific processing technique, the specific surface area of ​​the inner and outer pores of this honeycomb structure is coated with fire extinguishing agents such as sodium bicarbonate and potassium bicarbonate. These fire extinguishing agents are layered and applied, ultimately impregnating and encapsulating the expanded perlite, forming fire-fighting sand with effective fire extinguishing capabilities.

[0024] Example 2, Experimental materials: 20L fire-fighting sand (made of potassium bicarbonate), specific gravity 550 kg / m³. Two steel oil drums, A and B, with a diameter of 550 mm and a height of 500 mm, were used. To save fuel and simulate the water content of heavy oil with a wide boiling range, water was injected as a cushion layer. The water level in both oil drums was 200 mm, and the water temperature was 20 degrees Celsius. 25L of automotive engine oil was added to drum A, and 25L of transformer oil was added to drum B. The mixed liquid level in both oil drums was 315 mm. 20L of 3% fire-extinguishing foam liquid was taken from a foam fire truck. (Step 1): The automotive engine oil in drum A was ignited. After 5 minutes, the infrared thermometer showed a flame height of 720 mm and a temperature of 1510 degrees Celsius, with thick black smoke accompanying the billowing flames. 10L of fire-fighting sand (made of potassium bicarbonate) was poured in. The fire-fighting sand floated on the liquid surface, and the flame extinguished after 3 seconds. White water vapor and smoke were generated in the oil drum, reaching a height of 1500 mm. After extinguishing the fire, the oil temperature was measured at 125 degrees Celsius, and the water cushion temperature at 67 degrees Celsius. Firefighting sand was evenly distributed on the surface of the liquid in the drum, with no reignition observed. There was no boiling over or splashing. The 3% extinguishing foam solution was not used; the oil fire in the drum was extinguished. (Attached is a video recording of the uninterrupted fire extinguishing experiment 1) (Step 2): Ignite the transformer oil in drum B. After 5 minutes, the infrared thermometer showed a flame height of 810 mm and a temperature of 1650 degrees Celsius, accompanied by thick black smoke and billowing flames. Pour in 10 L of firefighting sand (made of potassium bicarbonate). The firefighting sand floats on the surface of the liquid, and the flame extinguishes after 5 seconds. White water vapor and smoke are produced in the oil drum, reaching a height of 1450 mm. The oil temperature was measured at 132 degrees Celsius, and the water cushion temperature at 71 degrees Celsius. Firefighting sand was evenly distributed on the surface of the liquid in the drum, with no reignition observed. There was no boiling over or splashing. The 3% extinguishing foam solution was not used; the transformer oil fire in the drum was extinguished. (Attached is video recording of the uninterrupted fire extinguishing experiment 2)

[0025] Conclusion: Based on the principles of specific gravity and buoyancy, fire-fighting sand impregnated with extinguishing agents (potassium bicarbonate) with a specific gravity less than 700 kg / m³ can be used as fire-fighting sand when heavy oil products are burning. The fire-fighting sand has a lower specific gravity than heavy oil products (such as engine oil and transformer oil), allowing it to float and cover the surface of the burning oil, reducing and covering the burning area. Upon contact with high temperatures, it releases carbon dioxide. This carbon dioxide gas is heavier than air and settles above the burning surface of the oil tank, occupying the lower part of the gas phase combustion space inside the tank. Due to the protective effect of the tank walls, the carbon dioxide gas is not dispersed by the wind. The generated water vapor forms a gas curtain above the liquid surface, isolating air, lowering the temperature of the combustion zone, and participating in fire extinguishing. It extinguishes the flames inside the oil drums and tanks before boiling over and splashing occur, controlling the occurrence of boiling over and splashing, and preventing the combustion of heavy oil products.

[0026] Fires involving flammable and combustible liquids are notoriously difficult and time-consuming to extinguish. A major challenge is the formation of extinguishing foam on the burning liquid surface; the foam either forms or dissipates, resulting in insufficient continuity, stability, and thickness of the coverage. The production and use of perlite fire-fighting sand will address this challenge. For fires involving ground leaks, flowing fires, or irregularly sized fires, fire-fighting sand (made from various extinguishing agents) can intercept, absorb, and cover the burning liquid, achieving the goal of extinguishing the fire.

[0027] Expanded perlite granules were soaked twice in a saturated potassium bicarbonate solution, stirred evenly, saturated leaching, and dried at low temperature to produce a material with a specific gravity of 700 kg / m³. 3 Firefighting sand that releases carbon dioxide and water vapor capable of extinguishing fires at a high temperature of 200℃ is shown in Table 2.

[0028]

[0029] 11 kg of expanded perlite, after being impregnated twice with a saturated potassium bicarbonate solution, leached, and dried at low temperature, contains 60 kg of potassium bicarbonate. At 200℃, it can decompose and release 7350 L of carbon dioxide and 6900 L of water vapor.

[0030] Example 3, Experimental Materials: 50L diluted asphalt. To avoid damage and contamination of the site, a 2.5*4.5 meter oil pan was prepared. 1500L of fire-fighting sand (made of sodium bicarbonate, specific gravity 450 kg / m³). A long-range fire-fighting spray device with patent number "2020201323415" and patent name "Long-range fire-extinguishing particle launching device" was used to spray the fire-fighting sand onto the fire location. The sand-blasting device was 21 meters away from the oil pan. To avoid accidents, a 25-ton foam fire truck from the fire and rescue brigade was requested as a backup. (Step 1) The diluted asphalt was poured into the oil pan and ignited, forming a full-area oil pan fire. After 5 minutes, the infrared thermometer showed a flame height of 3.7 meters and a flame temperature of 1360 degrees Celsius. Thick black smoke accompanied the flames. (Step 2) The sand-blasting cannon was started, and fire-fighting sand was sprayed towards the direction of the oil pan fire. As can be seen, the fire-fighting sand gradually covered the oil pan fire and its vicinity, significantly reducing the flame height and suppressing the fire. White water vapor and smoke were generated above and near the oil pan. The oil pan fire extinguished after 10 seconds. The backup foam fire truck was not used. (Attached is video recording of the uninterrupted fire extinguishing experiment 3) Conclusion: Fire-fighting sand impregnated with extinguishing agent (made of sodium bicarbonate) is effective for extinguishing ground-based liquid oil pan fires, flowing fires, and fires with irregularly sized areas. Because the raw material of the fire-fighting sand is expanded perlite, it has a high adsorption capacity for various flammable liquids, effectively blocking flowing fires, adsorbing flammable liquids, and covering the fire source. It effectively reduces the flame height, suppresses the fire, and releases carbon dioxide and water vapor to extinguish the fire when exposed to high temperatures. It can be used for long-range sandblasting fire monitors, spraying 600-800L per minute. This allows firefighters, fire trucks, pumps, and monitors to operate away from the fire scene, avoiding various unexpected dangers. However, the spraying distance and accuracy still need improvement.

[0031] Expanded perlite particles are repeatedly impregnated with a saturated sodium bicarbonate solution to produce a material with a specific gravity of less than 700 kg / m³. 3 Firefighting sand that releases carbon dioxide and water vapor at high temperatures, capable of extinguishing fires, has the following specific data:

[0032]

[0033] 11 kg of expanded perlite particles were impregnated with a saturated sodium bicarbonate solution, stirred until saturated, drained, and dried at low temperature. This process of impregnation, stirring, saturation, draining, and low-temperature drying was repeated four times to obtain the final fire-fighting sand, which contained 32 kg of sodium bicarbonate. It can decompose 4665 L of carbon dioxide and 4016 L of water vapor at 270℃.

[0034] Example 4: In fires involving polar, water-sensitive hazardous chemicals such as ketones, alcohols, esters, ethers, aldehydes, and amines, the polar liquid molecules absorb water molecules from ordinary protein foam, thus destroying the foam and exhibiting a strong dehydrating effect. These polar liquids possess extremely strong defoaming properties; even in the absence of fire, ordinary foam extinguishing agents cannot form and spread on the liquid surface. The effectiveness of alcohol-resistant foam extinguishing agents is also less than ideal. The foam rapidly collapses, and a large amount of water sinks to the bottom, increasing the liquid level and the risk of spillage from tank rupture. However, by utilizing the principles of specific gravity and buoyancy, the addition and use of perlite fire-fighting sand alters the formation and spreading conditions of the foam extinguishing agent. Firefighting sand impregnated with extinguishing agents, while having a lower specific gravity than various types of polar flammable liquids, can still float and cover the surface of flammable liquids. This provides a solid foothold for various types of foam, allowing foam or alcohol-resistant foam extinguishing agents to form and spread on a soft floating layer (bed) of firefighting sand of a certain thickness. This avoids direct contact between various extinguishing foams and the surface of flammable polar liquids, protecting the stability, effectiveness, and durability of the foam layer coverage. A certain thickness of firefighting sand, with its upward buoyancy and volume in various flammable liquids, replaces the surface tension, forming a soft floating layer (bed) of solid particles of a certain thickness on the liquid surface, indiscriminately supporting the formation and spread of any type of firefighting foam. The deployment and formation of this perlite sand soft floating layer (bed) can change the current situation where foam extinguishing agents cannot directly extinguish fires involving polar, water-sensitive hazardous chemicals such as alcohols, ketones, esters, ethers, aldehydes, and amines.

[0035] Prepare 500ml each of xylene, butyl acetate, n-butanol, cyclohexanone, 75% alcohol, and 95# gasoline in the laboratory. Pour each into a tempered glass container and label it with its name. (Step 1) Pour the fire extinguishing foam liquid into each container. The foam will immediately dissolve and disappear. Only a small amount of foam remains on the surface of the xylene and 95# gasoline containers, which will also dissipate quickly. (Step 2) Pour 100ml of fire sand into each container. The fire sand will float and cover the liquid surface, forming a fire sand layer with a thickness of 40-45mm. Looking down from above, only the fire sand particle layer is visible, and the surfaces of the various liquids are no longer visible. (Step 3) Pour the fire extinguishing foam liquid into each container. A foam layer will form intact, accumulating and covering the fire sand layer, with a foam layer thickness of 35-40mm. After 3 minutes, the foam layer coverage is basically intact. (See photos 1, 2, and 3.) Conclusion: All types of polar liquids exhibit extremely strong defoaming properties, and even in non-combustible conditions, they do not support the existence, formation, and spread of extinguishing foam on their liquid surfaces. Fire sand can form a continuous solid covering layer of a certain thickness on the surface of various polar liquids, providing a solid foothold for the extinguishing foam. This prevents direct contact with the polar liquid surface, protecting the foam layer and allowing it to form, spread to a certain thickness, and maintain its coverage for a long time.

[0036] Example 5, Experimental Materials: One steel oil drum, 550mm in diameter and 500mm in height. 25L of 95% alcohol. Two 20L drums of 3% fire-fighting foam liquid from a fire truck. 10L of fire-fighting sand (made of sodium bicarbonate), specific gravity 450 kg / m³. (Step 1): Pour 25L of alcohol into the steel oil drum and ignite it. After 3 minutes, the infrared thermometer showed a flame height of 360mm and a flame temperature of 575 degrees Celsius. (Step 2): Pour one of the foam liquids evenly into the burning alcohol drum. Intermittent foam coverage can be seen forming, which gradually dissipates as it forms. The flame height decreases, and the burning area tends to shrink. After 6-7 seconds, the foam gradually breaks down and dissipates, the foam coverage gradually collapses, until the foam completely disappears, the alcohol surface is exposed again, and the liquid surface in the drum resumes full-area combustion. (Step 3): Pour 10L of fire-fighting sand (made of sodium bicarbonate) evenly into the burning alcohol container. The fire-fighting sand gradually covers the alcohol surface, and the flame stream becomes finer as it passes through the sand layer. The burning area at the center of the liquid surface shrinks, and the flame height decreases. (Step 4): Pour another container of foam liquid evenly into the container. Fire-extinguishing foam forms and spreads on the fire-fighting sand layer, forming a foam layer 4-5cm thick. The flame in the alcohol container extinguishes after 3 seconds. The foam layer continues to continuously cover the granular layer on the liquid surface, maintaining a stable thickness, and there is no reignition. (Attached is a video recording of the uninterrupted fire extinguishing experiment 4)

[0037] Conclusion: In fires involving polar liquids, such as alcohol (ethanol), the strong defoaming properties of these liquids prevent fire-fighting foam from forming and spreading directly on the liquid surface, thus failing to create a long-lasting and stable effective coverage. Fire-fighting sand (made from various extinguishing agents) can be used as an intermediate medium to isolate, protect, and support the polar liquid and the fire-fighting foam liquid. Based on the principles of gravity and buoyancy, as long as the specific gravity of the fire-fighting sand is less than that of the burning liquid, it can float on the liquid surface and form a continuous and effective coverage. Upon contact with high temperatures, it releases carbon dioxide, inhibiting flame combustion. By replacing the surface tension with the volume and buoyancy of the fire-fighting sand layer, direct contact between the fire-fighting foam and the polar liquid is avoided. This provides the fire-fighting foam with a certain buoyancy and an uninterrupted solid foothold, indiscriminately protecting and supporting the formation and spread of various types of fire-fighting foam. It protects the fire-fighting foam from direct contact with the polar liquid, maintaining the thickness, stability, continuity, and durability of the foam layer. This reduces the overall amount of fire-fighting foam and fire-fighting water required for tank fires.

[0038] Example 6: The spraying of fire-fighting sand impregnated with extinguishing agent in a fire pump, cannon, and nozzle. The cannon tank contains 8000L of fire-fighting sand. The cannon is started and sprayed completely in 9.5 minutes at a pressure of 0.3 MPa. The spraying distance is 25-30 meters. This allows firefighters, fire trucks, and equipment to be kept away from the fire scene while projecting perlite fire-fighting sand onto the fire. (Video 1 of uninterrupted sandblasting experiment). A direct-flow fire hose is extended 60-80 meters from the cannon tank, with a spray rate of 350-500L / minute. Firefighting can be operated from any position and angle, offering higher accuracy. (Uninterrupted Sandblasting Experiment Video 2) Usage Method: For fire fighting and rescue operations involving a full-area fire in a storage tank, perlite fire-fighting sand that has been adsorbed and impregnated with extinguishing agents should be sprayed and placed first. A long-range fire-fighting spraying device with patent number "2020201323415" and patent name "Long-Distance Fire Extinguishing Particle Launching Equipment" should be used to spray the fire-fighting sand to the fire location. Both submerged spraying and surface placement are acceptable. In cases of tilting, sinking, or overturning hazards, the principle of specific gravity and buoyancy is utilized. Submerged spraying of perlite fire-fighting sand fills the concealed gaseous combustion space formed under the floating roof, and the upward buoyancy of the sand layer lifts the floating roof back to its original position. The fire-fighting sand will quickly accumulate on the liquid surface, forming a cover; the thicker the cover, the better the effect. The formation of a fire-fighting sand layer of a certain thickness fills, occupies, and reduces the space for gas-phase combustion within the storage tank, ensuring the tank's dry wall remains protected by the sand layer and is no longer exposed. This minimizes the heated area of ​​the dry wall above the liquid level, reducing heat absorption and preventing further temperature increases in the tank. The fire-fighting sand layer acts as an excellent liquid level stabilizer, effectively inhibiting and controlling turbulent combustion and reducing the intensity of combustion. It reduces the combustion area and direct heat radiation to the tank wall, protecting it from failure, deformation, and cracking. Simultaneously, the formation of the fire-fighting sand layer allows for the extraction and transfer of liquid from the burning tank to a safe area. While extracting and transferring the liquid, fire-fighting sand continues to be added and sprayed as the liquid level decreases, replacing the volume of flammable liquid transferred out with the volume of fire-fighting sand. This ensures the tank's dry wall remains continuously covered and protected by the fire-fighting sand layer. When perlite fire-fighting sand carries and impregnates the extinguishing agent, it decomposes upon heating, releasing carbon dioxide gas and water vapor. Carbon dioxide, being denser than air, settles above the surface of the burning liquid, occupying the gaseous combustion space within the storage tank. The generated water vapor forms a water curtain, lowering the fire temperature. The carbon dioxide and water vapor together inhibit flame combustion, reducing the intensity and height of the fire and stabilizing the combustion. Then, the spraying of extinguishing foam is initiated.

[0039] All liquids have surface tension, and fire-fighting foam floats on the surface due to its own surface tension and the surface tension of the liquid. In tank or pool fires, the liquid surface temperature is high, the flames are intense, and the liquid molecules are highly active. Turbulent combustion disrupts the surface tension and causes a loss of stability. Foam struggles to cover and spread on the burning liquid surface, and a large portion of the foam quickly bursts and sinks below the surface. To create a more stable foam layer, more fire trucks and monitors must be used, spraying larger quantities of foam. This raises the burning liquid level, potentially causing boiling over and splashing, creating a flowing fire and posing a potential hazard to firefighters and equipment during firefighting and rescue operations.

[0040] Example 7: Depending on the burning material, it can adhere to and impregnate various extinguishing agents. It is also suitable for extinguishing fires involving solid, water-sensitive hazardous chemicals. Perlite fire-fighting sand forms a stable heat-insulating layer, and the sand can penetrate and fill the gaps in the burning material. The small and dense gaps and pores between the sand particles perfectly match the structural principle of the flame-arresting core layer in a flame arrester. This allows a large flame to be divided and compressed into several small flame streams after passing through the dense sand layer, reducing the intensity and severity of combustion, effectively isolating air, and reducing the heat radiation generated by combustion. The effective dosage of extinguishing agent that is impregnated, adhered to, and carried is not limited by the specific gravity difference as in liquid fires; the higher the dosage, the better the effect. The extinguishing agent reacts when heated, preventing and inhibiting flame combustion. It is capable of high-dose spraying by large fire-fighting equipment. During the spraying process of fire pumps, monitors, and guns, it acts to smother, cover, peel off, and disperse the burning material, inhibiting combustion and extinguishing the fire.

[0041] Extinguishing Test of Expanded Perlite Firefighting Sand on Water-Resistant Solid Hazardous Chemicals. Step 1: Prepare 15L of expanded perlite firefighting sand (made with sodium bicarbonate). A steel oil drum, 550mm in diameter and 500mm in height, is used. Approximately 5kg of rolled sludge, 5kg of solid asphalt blocks, and 50 blocks of solid alcohol (approximately 2kg) are placed inside the oil drum. Step 2: Ignite the solid alcohol blocks with a long-handled igniter. The solid alcohol blocks burn successively and completely. An infrared thermometer shows a flame height of 370mm and a temperature of 550 degrees Celsius. At this point, the rolled sludge and solid asphalt blocks are not ignited. After 5.5 minutes, black smoke is produced, and the flame changes from light red to dark red and yellowish-red. The rolled sludge and solid asphalt blocks begin to burn. After 8 minutes, all the solid hazardous chemicals in the drum are fully burned. The infrared thermometer shows a flame height of 3.5 meters and a temperature of 1280 degrees Celsius. Thick black and yellow smoke, exceeding 20 meters in height, is also present. Step 3: Quickly add 15L of expanded perlite fire-fighting sand (made of sodium bicarbonate) into the burning oil drum. White smoke is rapidly produced, and the flame extinguishes after 5 seconds. Until the smoke dissipates, the expanded perlite fire-fighting sand is clearly visible, completely covering the inside of the drum, with no reignition. Conclusion: The prepared expanded perlite fire-fighting sand can be used in fires involving water-sensitive solid hazardous chemicals. It covers and penetrates into the gaps of the combustible solid, producing carbon dioxide and water vapor upon contact with high temperatures, causing the flame to extinguish rapidly and preventing reignition.

[0042] Through the above examples, we draw the following conclusions regarding the use of fire-fighting sand in fire suppression: In the rescue of liquid hazardous chemical fires, fire-fighting sand forms a continuous and stable covering layer on the liquid surface, reducing, hindering, and isolating the liquid surface from air contact, thus reducing the amount of flammable gas volatilization. The extinguishing agents impregnated and adsorbed by the fire-fighting sand release carbon dioxide and water vapor upon high temperatures. Carbon dioxide gas has a higher specific gravity than air and settles above the oil surface and below the gas phase combustion space inside the tank, rapidly cooling the tank and preventing flame combustion, thus playing a rapid fire-extinguishing role. The generated water vapor forms an air curtain, effectively reducing the temperature of the fire scene and preventing flame combustion. The dense, fine perlite particles, through the fire-retardant core layer structure, make the passing flame stream thinner and smaller, reducing the flame height and heat radiation range, and reducing the combustion intensity. It also reduces the temperature and speed of downward heat wave transmission formed by the combustion of wide-boiling-range liquids. The wall effect, where particles easily aggregate near the tank wall, reduces direct, close-range heating of the tank wall by the flame. The formation of a certain thickness of fire-fighting sand layer fills and occupies the gas-phase combustion space inside the tank, preventing direct, close-range heat radiation from the liquid combustion onto the dry wall of the storage tank, and slowing down the rate of temperature rise of the metal tank and the stored liquid. Simultaneously, the volume of fire-fighting sand injected into the tank replaces the liquid inside, protecting the tank wall and the liquid from direct heating and baking, while safely draining, transferring, and emptying the flammable liquid inside the tank, truly achieving a radical solution and reducing the potential hazard of a storage tank fire. While draining and transferring the liquid inside the tank, fire-fighting sand continues to be added and injected during the liquid level drop, replacing the volume of the transferred flammable liquid with the volume of fire-fighting sand, ensuring that the dry wall of the storage tank remains under the protection of the granular sand layer, avoiding high-temperature heat radiation, and ensuring that the tank wall does not fail, deform, or crack, effectively preventing pool fires and flowing fires in the storage tank area. This provides a safe and reliable measure for process fire extinguishing of storage tank fires. The volume and upward buoyancy of the liquid surface particle covering layer replace the surface tension, effectively supporting the rapid formation and spread of various fire extinguishing foams on a rough, continuous fire sand covering layer. This ensures a stable, durable, and durable foam layer that is not easily damaged or destroyed, preventing the risk of reignition. It reduces the amount of cooling water and overall foam required for firefighting, saving significant amounts of firefighters and equipment, while also reducing the total amount of fire wastewater and environmental pollution. It delays, reduces, and avoids the time and danger of boiling over and splashing in tank fires, effectively protecting the safety of firefighters and equipment. It also reduces the difficulty of launching a final assault on a tank fire. Utilizing the principles of specific gravity and buoyancy, it can also form a covering on water-soluble flammable and combustible liquids, such as ketones, alcohols, esters, ethers, aldehydes, amines, and other polar liquid hazardous chemicals. It is also suitable for fighting oil and electrolyte fires in various energy storage power stations. The formation of a rough, continuous, and stable solid particle floating bed provides a continuous and stable solid landing point for various fire extinguishing foams, preventing direct contact between polar liquids and the fire-fighting foam, protecting the foam from breakage and decay. This allows the fire-extinguishing foam layer to form, spread, and advance to all areas quickly and smoothly.It changes the previous situation where foam extinguishing agents could not be used in fires involving water-soluble flammable and other polar liquids, supporting the use of various types of fire-fighting foams in fire suppression without discrimination. It is suitable for covering and rescuing various types of liquid fires, and the liquid in the storage tank can be safely diverted, vented, and transferred, creating irreplaceable conditions for liquid fire fighting and rescue as well as process fire suppression.

[0043] The formation of a floating layer of fire-fighting sand on the liquid surface prevents dry powder extinguishing agents from sinking due to their excessive density. The dry powder extinguishing agents react fully within the flames on the floating sand layer, achieving optimal results. The floating sand layer also reduces the impact force on the liquid surface during fire hose and cannon operations, preventing the burning liquid from splashing and causing greater damage.

Claims

1. A type of fire-fighting sand for fires involving water-repellent liquid hazardous chemicals, characterized in that, The product includes expanded perlite particles, wherein the honeycomb structure of the expanded perlite particles contains an impregnated fire extinguishing agent in its inner and outer pores, and the fire extinguishing agent completely impregnates and coats the expanded perlite particles; The bulk density of the expanded perlite particles is 80-150 kg / m³, and the fire extinguishing agent is sodium bicarbonate or potassium bicarbonate. The method for manufacturing fire-fighting sand for water-repellent liquid hazardous chemicals is to soak expanded perlite particles in a saturated solution of fire extinguishing agent, stir evenly, drain after being fully soaked and saturated, and then dry at low temperature. After repeating the above steps multiple times, fire-fighting sand for water-repellent liquid hazardous chemicals is formed. The specific gravity of the fire-fighting sand used in the fire involving water-insensitive liquid hazardous chemicals is less than that of the water-insensitive liquid hazardous chemicals.

2. The fire-fighting sand for water-repellent liquid hazardous chemicals according to claim 1, characterized in that, The method for manufacturing the fire-fighting sand is as follows: Step 1, take several kilograms of expanded perlite, immerse the prepared expanded perlite particles in a saturated sodium bicarbonate solution at 60-80°C, and stir evenly. After the expanded perlite particles are fully saturated, drain them and dry them at a low temperature; the weight of the expanded perlite particles after the first impregnation and drying is 72.7% greater than that of the raw material; Step 2, impregnate the dried and weight-gained expanded perlite particles a second time in… The expanded perlite particles are stirred evenly in a saturated sodium bicarbonate solution at 60-80℃, fully soaked, drained, and dried at low temperature. The weight of the expanded perlite particles after the second soaking and drying is 145.4% higher than that of the raw material. In the third step, the expanded perlite particles after the second low-temperature drying are immersed for the third time in a saturated sodium bicarbonate solution at 60-80℃, stirred evenly, and drained and dried at low temperature after being fully soaked and saturated. The weight of the expanded perlite particles after the third drying is 218.1% higher than that of the raw material. In the fourth step, the expanded perlite particles after the third drying are immersed for the fourth time in a saturated sodium bicarbonate solution at 60-80℃. After the expanded perlite particles are fully soaked and saturated, they are drained and dried at low temperature. The weight of the expanded perlite particles after the fourth drying is 290.9% higher than that of the raw material.

3. The fire-fighting sand for water-repellent liquid hazardous chemicals according to claim 1, characterized in that, The method for manufacturing the fire-fighting sand involves impregnating expanded perlite with a saturated potassium bicarbonate solution. Several kilograms of expanded perlite and potassium bicarbonate saturated solution are taken. In step one, the expanded perlite particles are immersed in the saturated potassium bicarbonate solution at 60-80°C and stirred until fully saturated. After immersion, the particles are drained and dried at a low temperature. The weight of the expanded perlite particles after low-temperature drying is 272.7% heavier than the raw material. In step two, the expanded perlite particles, after the first low-temperature drying, are a second time impregnated in the saturated potassium bicarbonate solution at 60-80°C, stirred until fully saturated, drained, and dried at a low temperature. The weight of the expanded perlite particles after the second low-temperature drying is 545.4% heavier than the raw material.

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