Application of Fluoroprotein Foam Fire Extinguishing Agent in Underwater Spraying

Fluoroprotein foam fire extinguishing agent is prepared by adding appropriate amount of fluorocarbon surfactant on the basis of protein foam fire extinguishing agent. Due to the role of fluorocarbon surfactants, this fire extinguishing agent can not only have the fire extinguishing performance of protein foam fire extinguishing agent, but also can use the "underwater spraying" method to extinguish the fire in large oil storage tanks, and can also be combined with dry powder fire extinguishing agent. Its fire extinguishing speed is 1/3 faster than egg white foam fire extinguishing agent.

Oil storage tanks are usually very high and have a large amount of oil. After the explosion and fire, the fire is violent, the temperature is high, the radiation heat is strong, it is easy to spread and expand, and even continuous explosions, boiling spills, tank deformation and collapse, etc., making it difficult for personnel, vehicles, equipment and equipment to approach the battle, and rescue is very difficult and dangerous. In this case, the foam fire extinguishing system connected to the oil tank plays a vital role in initially controlling the fire and preventing its spread. Due to the high combustion temperature of the oil tank fire, the liquid jet fire extinguishing system is easily damaged, so the liquid foam jet fire extinguishing system is safer and more reliable. Because the underwater foam spray fire extinguishing system sprays the foam directly into the oil from the lower part of the storage tank through the pipeline, floats up under the buoyancy of the oil, and covers the burning oil surface for fire extinguishing, the underwater spray has a strong selectivity to the foam liquid, and the fluorine protein foam liquid is generally selected. When spraying fluoroprotein foam under liquid, the main problem that needs to be solved is how to prevent the foam from carrying too much oil and becoming a combustible foam and losing its fire extinguishing ability. The test shows that when water is injected into the foam, the amount of oil mist entrainment is mainly related to the foaming rate of the foam, the speed of the foam entering the oil and the thickness of the oil.

1. Reasonable design of foam foaming rate. The relationship between the foaming rate of the foam and the oil content was obtained by a cold spray test on a gasoline tank with a diameter of 2.7 meters and an oil layer thickness of 9 meters. Fluoroprotein foam can not only form a water film at the interface of foam and oil, but also wrap oil droplets in the foam to prevent oil evaporation and reduce the flammability of oily foam, because the fluorocarbon chain in the fluorocarbon surfactant molecule is both hydrophobic and highly oil-repellent. According to measurements, the gasoline content in the fluoroprotein foam can only burn freely when it exceeds 17%. In order to control the oil content of the foam within the non-flammable concentration range and consider its comprehensive fire extinguishing effect, the foaming rate of the foam should be controlled at about 3 times. Therefore, when the liquid is injected with fluorine protein foam to extinguish the gasoline tank fire, a special high back pressure foam generator should be used, and the working pressure should reach 7 × 105Pa.

2. Reasonable control of the speed of foam into the oil. The speed at which the foam enters the oil is an important technical parameter. It can be seen from the test that the speed of the foam into the oil increases, and the oil content in the foam also increases accordingly. This is because, as the flow rate increases, the agitation between the foam and the oil and the turbulence formed in the tank will also increase, resulting in an increase in the oil content in the foam. In order to reduce the oil content in the foam and ensure the fire extinguishing effect, it is necessary to limit the speed of the foam entering the oil. The test shows that for gasoline, low flash point crude oil and other Class A and B flammable liquids, the entry speed of fluorine protein foam with a foaming rate of 3 times shall not exceed 3 m/s; For Class C flammable liquids with high flash point or low volatility, such as kerosene and diesel, the foam entry speed can be slightly higher, but usually it cannot exceed 6 m/s. In addition, during water injection, the thickness of the oil in the storage tank is limited, for example, the oil thickness in the steam tank usually does not exceed 9m.