Discussion on the application of fluoroprotein foa

Brief discussion on the application of fluoroprotein foam extinguishing agent in oil tank fire suppression

[Abstract] fluoroprotein foam extinguishing agent is an important extinguishing agent for oil tank fire suppression, which has obvious advantages over protein foam extinguishing agent. In underwater injection, pay attention to the relationship between oil entrainment and foam foaming multiple, the speed of foam entering oil and the thickness of oil; Ensure the quality of foam formation and the efficiency of coverage in oil spray, and pay attention to the combination with dry powder to strengthen the fire extinguishing effect

[Key words] fluoroprotein foam oil tank fire oil entrainment foam quality coverage efficiency combined use

with the continuous development of China's economic construction and the deepening of industrialization, "the blood of industry" - the demand for oil and its products continues to grow, various oil storage areas continue to be established, and the storage capacity continues to increase. For this flammable and explosive liquid, various fire risk factors are both numerous and very complex. Once it explodes and catches fire, it will often form a large-scale fire, and the fire is also extremely fierce. Therefore, fighting oil fires has become a difficult problem for the majority of fire workers. This paper puts forward some personal views on the application technology of foam extinguishing agent in oil tank fire fighting, although fluoroprotein foam is still used in some occasions

I. characteristics of fluoroprotein foam liquid

to fight oil tank fires, it often requires a lot of fire-fighting technical equipment and a lot of human and material resources. In terms of fire extinguishing agents, in addition to water, foam fire extinguishing agents are also essential "ammunition". In many cases of oil tank fire fighting in China, fluoroprotein foam extinguishing agent has played a very important role

fluoroprotein foam extinguishing agent is a kind of foam extinguishing agent developed in the 1960s to overcome the shortcomings of protein foam extinguishing agent. It is made of protein foam extinguishing agent as the base material and an appropriate amount of "6201" preformed liquid. (Note: "6201" preformed liquid, also known as FCS solution, is an aqueous solution prepared by "6201" fluorocarbon surfactant, isopropanol and water at the mass ratio of 3:3:4). 6% fluoroprotein foam extinguishing agent contains 1% of "6201" preformed liquid, and 3% fluoroprotein foam extinguishing agent contains 2% of "6201" preformed liquid

the extinguishing principle of fluoroprotein foam extinguishing agent is basically the same as that of protein foam extinguishing agent, but due to fluorocarbon Table 1 Because there is no resistance surface active agent that liquid raw materials must overcome in the closed mold, its fire extinguishing performance is greatly improved. Compared with protein foam extinguishing agent, fluoroprotein foam extinguishing agent has obvious characteristics: first, the surface tension and interfacial tension are significantly reduced; Second, foam has good fluidity and fast fire extinguishing speed; Third, fluoroprotein foam has strong resistance to oil pollution, and can extinguish large oil tank fires by means of underwater injection; Fourth, it can be combined with dry powder. Therefore, fluoroprotein foam extinguishing agent is widely used in the fire fighting of large oil storage tanks

II. Application of fluoroprotein foam fire extinguishing agent in underwater spraying

oil storage tanks are generally tall and have a large oil storage capacity. After the explosion and fire, the fire is fierce, the temperature is high, the radiant heat is strong, and it is easy to spread and expand, and even continuous explosion, boiling and splashing, tank deformation and collapse, etc. occur. Personnel, vehicles, equipment and equipment are difficult to approach and fight, so it is extremely difficult and dangerous to put out the fire. In this case, the foam fire extinguishing system attached to the oil tank plays a vital role in controlling the fire in the initial stage and preventing it from spreading. Due to the high combustion temperature of oil tank fire, the liquid foam sprinkler system is easy to be damaged. Therefore, the liquid foam sprinkler system is more safe and reliable. Because the underwater foam spray extinguishing system is to spray foam directly into the oil from the lower part of the tank through the pipeline, float up under the buoyancy of the oil, and cover the liquid level of the burning oil to extinguish the fire, the underwater spray has strong selectivity for foam liquid, and fluoroprotein foam liquid is generally selected. When spraying fluoroprotein foam underwater, the main problem to be solved is how to prevent the foam from carrying too much oil products to become combustible foam and losing the fire extinguishing ability. The test shows that when foam is sprayed underwater, the entrainment of oil is mainly related to the foaming multiple of foam, the speed of foam entering the oil and the thickness of oil

1. Reasonably design the foaming multiple of foam. The relationship between the foaming multiple and the oil content of foam obtained from the cold spray test of a gasoline tank with a diameter of 2.7 meters and a thickness of 9 meters is shown in the figure

fluoroprotein foam can not only form a water film at the junction of foam and oil, but also wrap oil droplets in foam to prevent oil evaporation and reduce the flammability of oil-containing foam because the fluorocarbon chain in fluorocarbon surfactant molecules has both hydrophobicity and strong oil repellency. According to the determination, fluoroprotein foam can burn freely when the gasoline content is more than 17%. In order to control the oil content of foam within the non combustible concentration and consider its comprehensive fire extinguishing effect, it is appropriate to control the foaming multiple of foam at about 3 times. Therefore, when injecting fluoroprotein foam under the liquid to put out the fire of gasoline tank, a special high back pressure foam generator must be used, and the working pressure must reach 7 × 105Pa。

2. Reasonably control the speed of foam entering the oil. The speed at which foam enters the oil is an important technical parameter. It is known from the test that the oil content in foam increases with the increase of the speed of entering oil products. This is because, with the increase of flow rate, the agitation between foam and oil products and the turbulence formed by oil products in the oil tank also increase, resulting in the increase of oil content in foam. In order to reduce the oil content in foam and ensure the fire extinguishing effect, the speed of foam entering oil products must be limited. The test shows that the entry speed of fluoroprotein foam with 3 times of foaming ratio cannot exceed 3m/s for class A and class B flammable liquids such as gasoline and low flash point crude oil; For class C flammable liquids with high flash point or low volatility, such as kerosene, diesel oil, etc., the entry speed of foam can be slightly higher, but generally not more than 6m/s. In addition, there are certain restrictions on the thickness of oil in the storage tank during underwater injection. For example, the thickness of oil in the gasoline tank is generally not more than 9 meters

III. application of fluoroprotein foam extinguishing agent in oil surface spraying

in extinguishing oil tank fires, in addition to using the fixed fire-fighting facilities attached to the oil tank, operating foam guns, cannons, hook tubes and other fire-fighting technical equipment to extinguish the fire is the main aspect of the whole combat action. The technology of using fluoroprotein foam extinguishing agent to spray oil surface mainly includes two aspects: one is to ensure the quality of foam formation, that is, the water is well mixed with foam liquid, and the foaming ratio is high. Specifically, the foaming ratio of foam is not less than 6 times of the mixed liquid; The second is to ensure the efficiency of foam coverage, that is, to spray all the foam on the oil surface as far as possible, so as not to cause artificial mechanical damage and waste to foam

in terms of ensuring the quality of foam formation, the following links are mainly involved:

1. The adjustment of various pointers and valves should be coordinated. When using foam gun, gun and hook pipe to spray foam, the position of the pointer on the foam mixer should be consistent with the model of the foam gun, gun and hook pipe used. For example, when using a 25L foam pipe gun, the position of the pointer on the foam mixer should be adjusted to 25 (pH4); If 50L is used, the position of the pointer should also be adjusted to 50 (pH8), and so on. Don't mistakenly think that the pointer on the foam mixer is to adjust the occurrence multiple of foam. When foam is not formed well, adjust the pointer randomly, and the worse the result is. The valve at the pump outlet and the closing and opening valves on the foam gun should be completely opened. In addition, pay attention to opening the top cover of the foam tank to allow air to enter, so as to avoid the formation of vacuum in the foam tank and the failure of foam liquid delivery

2. Ensure the working pressure of various guns, guns and hook tubes, so that the mixed liquid can be fully mixed with air. The air mechanical foam currently used by fire forces is mainly formed by the full mixing of mixed liquid and air under the action of machinery. In order to fully mix the mixed liquid with air, it must have sufficient mechanical effect, and all kinds of guns, cannons and hook tubes must have sufficient inlet working pressure. The working pressure of the pump should be adjusted according to the needs of the inlet working pressure of various foam guns, cannons and hook tubes, so that the mixed liquid and air can be fully mixed

in terms of ensuring the efficiency of foam coverage, there are mainly the following problems that need to be paid attention to:

1. Mechanical impact should be minimized. Due to the strong mechanical impact, a large number of foam will burst, so that the foam will be destroyed. Therefore, when spraying foam, it should be sprayed directly on the tank wall or other objects, not on the oil surface. It should be sprayed along the tank wall close to the oil surface as far as possible, so as to minimize the damage caused by the mechanical action of foam

2. Try to avoid high temperature damage. Since high temperature will cause certain damage to foam, when spraying foam, try to avoid too much foam flowing through the high-temperature tank wall, and pay attention to avoiding flames

3. Try to speed up the flow speed. The use of foam to fight oil fires mainly depends on the flow of foam itself to cover, so as to achieve the fire-fighting effect. In order to speed up the flow of foam, the spray gun can be properly waved to make the foam extinguishing effect better

a large number of fire extinguishing tests show that the reasonable selection of two or more fire extinguishing agents for joint fire extinguishing can combine the respective advantages of fire extinguishing agents, and the effect is better than that of using one fire extinguishing agent alone. The technology of using fluoroprotein foam fire extinguishing agent and dry powder fire extinguishing agent to put out oil tank fires is a fast, reliable and efficient fire extinguishing method to put out large-area oil fires, which can minimize fire losses and obtain the best social and economic benefits. The fire extinguishing technology of fluoroprotein foam combined with dry powder can not only give play to the advantages of the thoroughness of foam fire extinguishing and the rapidity of dry powder fire extinguishing, but also overcome the defects of the slow fire extinguishing of foam and the easy re ignitability of dry powder fire extinguishing, and achieve better fire extinguishing effect. This is because the surface tension of fluoroprotein foam is lower than that of fuel, which can not only resist 15N rupture caused by fuel, but also resist dry powder pollution and damage, so it can achieve the best effect of fire extinguishing

of course, when fluoroprotein foam is combined with dry powder, only by choosing a better combination method, can we give full play to the respective advantages of fire extinguishing agents and achieve better fire extinguishing effect. When foam and dry powder are sprayed at the same time, the fire extinguishing effect is not ideal, which may be caused by the mutual interference between foam and dry powder when they pass through the flame area. When a certain fire extinguishing agent is used for a period of time and then sprayed at the same time, the effect is better than using fluoroprotein foam alone. The test shows that the best effect can be achieved when the foam is sprayed for 5 seconds and the foam and dry powder are sprayed at the same time when the fire is basically half controlled. This combined method achieves the purpose of using the least amount of extinguishing agent to extinguish the fire