Foam extinguishing agent is an effective fire extinguishing agent for fighting flammable flammable liquids. It mainly generates a condensed foam floating layer on the surface of the liquid and acts as a suffocation and cooling.
1 . Classified by mixing ratio
Foam fire extinguishing agent can be divided into 1.5% type, 3% type, 6% type, etc. according to the ratio of the foam liquid mixed with water .
2 . According to foaming multiple
Foam extinguishing agents can be divided into low-expansion foam extinguishing agents, medium-multiple foam extinguishing agents and high-expansion foam extinguishing agents according to their foaming multiples. Foam multiples of low-expansion foam fire extinguishing agents are generally 20
Below the fold, the expansion ratio of the mid-multiple foam extinguishing agent is between 20 and 200 times, and the expansion ratio of the high-multiplier foam extinguishing agent is generally between 200 and 1000 times.
3 . Classified by use characteristics
Foam extinguishing agents can be classified into Class A foam extinguishing agents and Class B foam extinguishing agents according to their use places and characteristics . Class B foam extinguishing agents can be further divided into non-water soluble foam extinguishing agents (such as protein foam extinguishing agents and fluoroprotein foam extinguishing agents. Agents, "light water" foam extinguishing agents) and anti-solvent foam fire extinguishing agents (gel-type anti-dissolution foam extinguishing agents, water-forming film-forming anti-foam agents, fluoroprotein anti-foam agents, film-forming proteins Agents, film-forming fluoroprotein anti-foam foam extinguishing agents, medium-strength anti-foam foam extinguishing agents).
4 . Classified by matrix of synthetic foam
Foam extinguishing agents can be divided into protein foam extinguishing agents and synthetic foam extinguishing agents. Protein foam extinguishing agents include common protein foam fire extinguishing agents, fluoroprotein foam fire extinguishing agents, film-forming fluoroprotein foam fire extinguishing agents, and anti-solvent and film-forming protein anti-dissolving foam extinguishing agents; synthetic foam extinguishing agents mainly have high-multiple foam extinguishing agents. , High, medium and low general-purpose foam extinguishing agents, water-based film-forming foam extinguishing agents, water-soluble film-forming extinguishing agents, Class A fire foam.
Common foam fire extinguishing agent
First, chemical foam fire extinguishing agent
1 . Components and effects
Mainly still aluminum sulfate, sodium bicarbonate two agents as a blowing agent, and added a fluorocarbon surfactant, hydrocarbon surfactant composition of synergist.
2 . performance
Has a small viscosity, fluidity and self-sealing ability, high fire extinguishing efficiency. The fire extinguishing efficiency is 2 to 3 times that of the same amount of YP type chemical foam fire extinguishing agent ; and all synthetic raw materials are used, which are not easily deteriorated and the storage period is longer.
Fire extinguishing principle
When used, try to mix the aqueous solution of acidic agent and alkaline agent. The carbon dioxide produced in the reaction forms a lot of fine bubbles in the solution on the one hand; at the same time, the pressure in the fire extinguisher rises quickly and the generated foam is sprayed from the nozzle. . The colloidal aluminum hydroxide generated by the reaction is distributed on the bubble film, so that the foam has a certain viscosity, and is easy to adhere to the combustion, and enhances the thermal stability of the foam. The fluorocarbon surfactant in the agent can make the fire extinguishing The surface tension and critical micelle concentration of the agent solution are reduced, and it is easy to form bubbles; at the same time, the diffusion coefficient of the solution is positive, and a water film can be formed on the surface of the water-insoluble flammable liquid; the hydrocarbon surfactant can make the foam It is stable and has a certain auxiliary effect on film formation.
5 . Storage method
Internal and external agents must be packaged separately. The internal and external doses required for each fire extinguisher must be a minimum unit of packaging. All plastic and polyvinyl chloride plastic bags should be packaged, and then packaged in cartons or wooden boxes. Avoid moisture and exposure during transportation.
Chemical foam extinguishing agents should be stored in a cool shade. In dry warehouses; internal agents and external agents should be stacked separately, stacking should not be too high.
6 . Validity period
The chemical foaming agent is filled in a fire extinguisher after being formulated and is valid for one year.
The foam of chemical foam fire extinguishing agent is produced through the chemical reaction of the aqueous solutions of the two agents. Because of its poor fire extinguishing effect, strong corrosion, short shelf life, harmful to the human body and the environment, it has been used for many years in China.
Second, air foam fire extinguishing agent
Foam of air foam fire extinguishing agent is generated by stirring. According to its foaming multiple can be divided into low multiple foam, medium multiple foam and high multiple foam three categories. According to the type and application of foaming agent, low-multiple foam extinguishing agents can be divided into five types: protein foam, fluoroprotein foam, aqua-film foam, anti-solvent foam and synthetic foam fire extinguishing agent.
1. Protein Foam
Protein foam extinguishing agents are the most basic type of foam. It is divided into animal protein and vegetable protein. Its main components are water and hydrolyzed protein. It is made of additives such as stable, antifreeze, slow release, antiseptic and viscosity control. It is a dark brown viscous liquid with Decomposition of natural protein odors. The foam liquid also contains a certain amount of inorganic salts, such as sodium chloride, ferrous sulfate and the like. Usually stored in drums or storage tanks, by the pressure flow proportioner for fire fighting by 6: 97 mixing ratio to form a mixture, the mixture flows through the intake air when the foam tube or foam generators gun: 3 or 94 , And after the mechanical stirring, the advantages of foam, sprayed to the combustion area to implement the fire.
In 1922 , Jennings of the American Standard Oil Company injected animal glue and ferrous sulfate onto the surface of gasoline to prevent it from evaporating and catching fire. This was the first time in the world that protein foam was used in firefighting. Later, Weissenbauer and Speyer of Germany found that protein hydrolysates are the best foam extinguishing agents. They placed the protein hydrolyzate and the aqueous solution of sulfuric acid as two aqueous solutions. When used, they were mixed and inhaled air was stirred and foamed. After that, they added ferrous sulfate to the protein hydrolysate and used it as a concentrate to develop the current protein foam. They concentration of 5% and freshwater and seawater mixture composition, the foam generating 8 times, can be stably stay in the oil surface. Stama's company in Hamburg, Germany, still sells this foam.
( 1 ) Fire extinguishing principle
The proportion of air foam generates light (typically between 0.1 to 0.5), good fluidity, strong anti-burn, not break up easily, quickly forming a capping layer non-water soluble liquid surface will quickly extinguish the fire . Because the protein foam can also adhere to the vertical surface, it can also save the fire of the general solid material. At present, protein foam is mainly used to fight oil fires.
( 2 ) Features
The advantages of protein foams are mainly available raw materials, simple production processes, low cost, good foam stability, low water quality requirements, and good storage performance. However, compared with other foams, foams have poor flow properties and have low resistance to oil contamination. They cannot be used for submerged firefighting or combined with dry powder fire extinguishing agents. Destroyed) is mainly used to rescue oil fires.
( 3 ) Application range
It is mainly used to extinguish general non-water soluble flammable and flammable liquid fires, and it can also be used to fight fires of general combustible solid materials. Due to its good thermal stability and covering properties, it is also widely used in fire extinguishing of oil storage tanks or injecting foam into unfired tanks to prevent ignition of radiant heat from nearby fire tanks. Use protein foam to rescue crude oil. When heavy oil storage tanks are in a fire, be aware of possible oil spills or splashes.
2. Fluorine foam fire extinguishing agent
The National Foam Company of the United States developed a fluoro-protein foam, AER-O-FOAMXL , in 1965 . The fluorinated protein foam has good fluidity and is not easily defoamed when contaminated with oil, and can be used in the form of submerged injection. Immediately after the National Foam Company, the Angus and ICI companies in the UK also made Fluorin-Protein Foam Fluid, which was sold on the market with FP-70 products. In Europe and America, after the introduction of fluoroprotein foam, it quickly replaced protein foam as the main extinguishing agent for protecting large tanks.
( 1 ) Components
Adding the " 6201 " solution to the protein foam can be used as a fluorin-protein foam fire extinguishing agent. “
6201 " Precast solution, also known as FCS solution, is an aqueous solution prepared from " 6201 " fluorocarbon surfactant, isopropyl alcohol and water in a mass ratio of 3 : 3 : 4 .
"6201 fluorocarbon surfactant by weight of 6% and 3% fluorine type foam protein percentage was 0.33% and 0.66%, respectively. Thus, the two types of F protein foam liquid, produced according to a predetermined mixing ratio fluorine protein foam, the content of which is 6201 fluorocarbon surfactant are 0.0196% (wt%)
( 2 ) Fire extinguishing principle and foam characteristics
The principle of fire extinguishing is basically the same as that of protein foam. However, due to the effect of the fluorocarbon surfactant, its aqueous solution and foam properties have undergone significant changes, thereby improving the fire extinguishing efficiency.
1 The surface tension and interfacial tension of the aqueous solution decreased significantly: Experiments have shown that the aqueous solution prepared by mixing the protein foam solution with water at the specified mixing ratio has a surface tension of about 46 × 10 - 5N / cm , and the fluoroprotein foam is formulated according to the prescribed mixing ratio. Extinguishing agent aqueous solution, the surface tension at the " 6201 ' ' and OBS content of 0.015% is only about 21 × 10 - 5N / cm . Moreover, " 6201 " and OBS can also reduce the fire extinguishing agent solution and oil between The interfacial tension, the reduction of surface tension and interfacial tension, all mean that the energy required to produce the foam is relatively reduced.
2 Foam is easy to flow: The critical shear stress of the foam is directly related to the fluidity of the foam. The smaller the shear stress, the better the fluidity of the foam. Experimentally determined that the critical shear stress of the protein foam is about 200 × 10 - 5N / cm ; and the critical shear stress of the fluoroprotein foam is only 100
× 10 - 5N / cm . Thus, the fluorinated protein foam is much more fluid than the protein foam. The fluorinated protein foam is fired with a thin layer of foam, that is, it can quickly cover the oil surface, and the foam is relatively strong and not easy to be destroyed; even if it is broken, it can be quickly self-propelled because of its good fluidity and self-healing properties. heal.
3 foam oleophobic ability: When fire extinguishing, often due to foam injection and oil surface impact, so that part of the foam dip into the oil, and entrain a certain amount of oil and then float to the oil surface. When the protein foam containing - fuel timing, i.e., free to burn, thus not be used in liquid ejection. When the fluoroprotein foam is extinguished, since the fluorocarbon chain in the fluorocarbon surfactant molecule has both hydrophobicity and strong oleophobicity, a water film can be formed at the interface between the foam and the oil, and the oil dripping package can be formed. In the foam, the evaporation of the oil is prevented and the flammability of the oil-containing foam is reduced. Experiments have shown that when the amount of gasoline contained in the protein foam exceeds 2 %, it is flammable, and when it reaches 8.5% , it can be burned freely; and when the content of gasoline in the fluoroprotein foam needs to be as high as 23% or more, it can be burned freely.
4 Good compatibility with dry powder: Protein foam cannot be combined with normal dry powder.
Because the moisture-proofing agent ( such as magnesium stearate ) used in the dry powder has a great destructive effect on the foam, the foam will be quickly destroyed and disappear when it comes into contact. Therefore, the protein foam can only be combined with specially-made powder use. The fluorinated protein foam has the ability to resist dry powder destruction due to the effect of the fluorocarbon surfactant. When the protein foam contains 0.01% of 6201 or OBS , it has a clear ability to resist the destruction of dry powder; when the content of " 6201 ' or OBS reaches 0.015 to 0.02% , it has a good combination with dry powder. Therefore, fluorine Protein foam fire extinguishing agent can be used together with various dry powders, and can achieve good fire-extinguishing effect.Dry-powder extinguishing agent extinguishes fire quickly and can quickly suppress the fire;foam covers the oil surface and can prevent re-ignition. When you use it, give full play to your strengths and you can quickly extinguish the fire.
( 4 ) Application area
It is the same with a protein foam fire extinguishing agent, mainly used for fighting various non-flammable water-soluble, flammable liquids, and - some of the combustible solid fire. It is widely used to extinguish large-scale storage tanks ( liquid injection ) , bulk storage, transfer relays, production and processing equipment, oil terminals and aircraft fires. Its use, storage requirements and the same protein foam.
3. Aqueous film forming foam extinguishing agent
Aqueous film-forming foam was invented in the United States. From 1946 to 1952 , the Weissman of the US Naval Technical Institute discovered in the research group that the fluorosurfactant has both water repellency and oil repellency. The study's Chabu study used fluorosurfactant as an extinguishing agent and developed a combined system that uses it together with dry powder fire extinguishing agents. The aqueous solution of the fluorosurfactant precipitated from this foam forms a film on the surface of the oil, floats on it, suppresses the occurrence of steam after fire extinguishing and prevents re-ignition. Because it forms a light, water-based film on the surface of the oil, the U.S. Navy called it a light-water foam and was patented in 1964 .
( 1 ) Components
It consists of fluorocarbon surfactants, hydrocarbon surfactants and additives ( foam stabilizers, antifreezes, co-solvents, thickeners, etc. ) and water. The fluorocarbon surfactant is the main component thereof, which accounts for 1 to 5 %; it may be one kind or a mixture of various surfactants. The hydrophilic groups may be cationic or anionic, amphoteric or non-ionic, and the most used are anionic. Aqueous film-forming foam extinguishing agents also contain polyethylene oxide 0.1 to 0.5 to improve the foam's ability to resist re-ignition and self-sealing.
The content of non-fluorosurfactant used in the aqueous film forming foam extinguishing agent is 0.01 to 0.5 %. It can not only increase the foam expansion and stability, but also reduce the interfacial tension between the aqueous film-forming foam aqueous solution and the oil, enhance the affinity with the oil, and contribute to the formation and diffusion of the water film, making a part of Some fluorocarbon surfactants that do not form a diffusion film can also be better filmed to form a strong, water-containing film.
The solvent in the aqueous film-forming foam is ethylene glycol butyl ether, diethylene glycol butyl ether, etc., and the amount thereof is 5 to 40 %. They have a solubilizing effect on each component, and can enhance the foam performance, reduce the freezing point of the foam liquid, and help the foam formation.
( 2 ) Fire extinguishing principle
When fighting fires in petroleum products, they rely on the dual role of foam and water film, and the foam plays a leading role.
1 The fire extinguishing function of the foam: Due to the effect of the fluorocarbon surfactant and other additives in the aqueous film-forming foam, it has a lower critical shear stress than the fluorinated protein foam ( its critical shear stress is only 60 × 10 - 5N / cm (left and right ) , when the foam is sprayed onto the oil surface, the fluidity is very good, it quickly spreads out on the oil surface, and quickly extinguishes the fire in conjunction with the action of the water film.
2 water film extinguishing effect; Aqueous film-forming foam is characterized by the formation of a thin layer of water on the surface of the oil, this is due to the combined effect of fluorocarbon surfactants and non-fluorinated surfactants.
This layer of water film can isolate the oil from the air, prevent oil and gas from evaporating, and is more conducive to bubble flow and accelerate fire extinguishing. However, the water film alone cannot effectively extinguish the fire. In fact, the fire-fighting effect of a film-forming foam is that when the foam is sprayed onto the burning surface, the foam spreads on the surface of the oil and forms a layer of water on the surface of the oil, which suppresses evaporation of the oil. It is isolated from the air and allows the foam to quickly flow to areas that have not yet been directly injected to further extinguish the fire.
4. Resistant foam fire extinguishing agent
Water-soluble flammable liquids, such as alcohols, esters, ethers, aldehydes, organic acids, and amines, due to their strong molecular polarity, can absorb large amounts of moisture in the foam and cause the foam to break down quickly without extinguishing the fire. Can not use the protein foam, fluoroprotein foam and "light water" foam to save such liquid fires, but must use anti-soluble foam to save.
The main types of fire resistant foam agents are: â‘ base to hydrolyze the protein material, an anti-insoluble metallic soap is added extinguishing agent made of zinc, cadmium, aluminum, organic salts of fatty acids, has been eliminated; â‘¡ to hydrolyse protein or synthetic The surfactant is a foaming agent, a high-molecular-type foam-resistant foam extinguishing agent made by adding a natural polymer compound such as alginate; 3 a thixotropic foam-removing agent extinguished by a fluorocarbon surfactant and a polysaccharide 4 Fluorine-based foam-resistant foam extinguishing agent made by adding special fluorocarbon surfactant and various metal salts to protein foam liquid; 5 Foam-resistant foam fire extinguishing agent made of silicone surfactant .
Principle of fire extinguishing: When the original liquid is diluted with water, no precipitate is produced, and the mixture is a transparent, homogeneous liquid. Upon contact with the surface of the water-soluble solvent, the foam reacts immediately, capturing the moisture in the foam layer and forming a uniform, viscous film that is insoluble in water and insoluble in the solvent. So as to effectively prevent the destruction of foam by water-soluble solvent and improve the stability and durability of the foam. When the fire extinguishes, the foam quickly covers the liquid surface, or adheres to the solid surface of the incinerator, forming a tight covering, thereby insulating the air from extinguishing the fire.
Application: Anti-foaming foam is mainly used to save ethanol, methanol, acetone. Ethylene acetate and other general water-soluble flammable, flammable liquid fire. Should not be used to fight low-boiling organic solvents such as aldehydes, ethers, organic acids, and amines. Although it can also save general oils and solid fires, it is generally not adopted because of its high price.
Features: This fire extinguishing agent has rich source of raw materials, simple manufacturing process, low price, small foam corrosion, long period of validity, and can be pre-mixed with water, and the conveying distance of mixed liquid is not limited. Can be used for ordinary foam fire extinguishing equipment, but also for fixed, semi-fixed or mobile fire extinguishing systems. The foam cushioning device still needs to be installed during use.
Fire extinguishing principle: When fire is extinguished, foam can form a layer of gel containing bubbles on the surface of polar solvents. This film can effectively prevent the destruction of polar solvents and achieve the purpose of covering fire extinguishing.
Usage: General fire extinguishing equipment can be used for premixing; if U -type applicator is used , the foam will flow along the wall of the container 40cm away from the liquid surface . In actual use, the mixing ratio of 9 % and 6 % can achieve better fire extinguishing effect.
Scope of application: This anti-solvent foam extinguishing agent is mainly used to extinguish liquid fires such as methanol, ethanol, ether and acetone.
5. High multiple foam fire extinguishing agent
In the 1960s , the high-magnification bubble and its application technology developed rapidly in the United Kingdom, the United States, Sweden, Japan and other countries. It is based on synthetic surfactants and can deliver 500 to 1000 times the foam through a high-intensity foam generator, rapidly filling the protected area and space with large amounts of foam.
Insulation is performed by burning oxygen (air) necessary for combustion. In addition, high multiples also have the ability to cool and prevent heat transfer in the fire. China has developed fresh water type, seawater type, smoke-resistant and temperature-resistant high-power foam series products since the 1970s , and developed corresponding fixed fire-extinguishing systems for above-ground and underground building fires, gradually realizing standardized and serialized application technologies.
( 1 ) Components
Generally by the foaming agent, Yan set agent, solvent, antifreeze, hard water softener, additives and other components.
( 2 ) Main performance indicators
Its appearance should be homogeneous liquid, no obvious toxicity, with biodegradability; its use temperature range: ordinary type is - 5 ~ - 40 °C , cold-resistant type is - 10 ~ 40 °C , ultra-cold resistant type - 20 ~ 40 °C .
( 3 ) Fire extinguishing principle
A high-strength foam fire extinguishing agent aqueous solution is generated by a high-expansion foam generator and its foaming factor is as high as 200 to 1,000 times. Bubble diameter is generally more than 10mm . Due to its large volume expansion and the high foaming capacity of the high-expansion foam generator ( large-scale foam can produce more than 1000m3 in 1 min ) , the foam can quickly fill the fire space, covering the combustion and insulating the combustion from the air. The large amount of water vapor generated after the foam is heated absorbs heat to a large extent, causing the temperature in the burning zone to drop abruptly, diluting the oxygen content in the air, preventing the heat conduction in the fire field, convection and heat radiation, and preventing the spread of fire. Therefore, the high-expansion foam fire extinguishing technology has the characteristics of small supply intensity of the liquid mixture, large foam supply, rapid fire extinguishing, safety and reliability, low water stain loss, and simple on-site treatment after fire extinguishing.
( 4 ) Application range
It is mainly used to fight water-insoluble flammable, flammable liquid fires and general solid material fires ( such as fires from oil tanks to fire banks or flammable liquids leaking from rotating machinery, etc. ) , and warehouses, hangars, etc. Basements, underground passages, mines, ships and other limited space fires. When the tanks of cryogenic liquids, such as liquefied natural gas, leak, they can also be applied with high-strength foams to prevent the vapor from evaporating and catching fire.
Because of its small specific gravity and good fluidity, it can be transported to a certain height or far away place to extinguish the fire by the action of the bubble-generating airflow through appropriate pipelines.
As the oil tank catches fire, the rising air current above the oil tank lifts very much, but the proportion of the foam is very
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