In recent years, petrochemical fire accidents have occurred from time to time across the country, causing major property losses and casualties, and have caused many adverse effects on the society. The raw materials and finished products that are stored, used, or produced by petrochemical companies are extremely flammable, explosive, toxic, and corrosive. Once an accident occurs, it not only threatens human life safety, but also pollutes the atmosphere and the water and soil environment.
First, the characteristics of oil depot fire
1, a sudden fire broke out in an instant
The flash point of petroleum product oil vapors is low, and a light friction or an invisible weak Mars can cause combustion or explosion.
Once the argan oil pool catches fire, if the rescue measures are ineffective, it will quickly spread and it will easily cause a large area of ​​fire. The route of its spread may be the following: along the route of leaking oil spills; oil vapour along the oil depot is spread to the direction of diffusion of the vapour; after the explosion is caused, the explosion wave pushes the flying fire to spread around; the explosion causes the container Cracking, spillage of oil, the spread of fire along the direction of the flow of oil products; the flame caused by heat radiation in the vicinity of the oil product; under the wind, the fire spread to the direction of the wind.
2. Combustion and explosion threatens four neighbors
(1) Explosions cause combustion. Once the product oil vapor evaporates and mixes with air, it can easily form an explosive gas mixture. This type of gas will explode immediately in the event of an open flame or spark with ignition energy. The high temperature and high pressure shock generated by the explosion will cause the oil product to spill out and evaporate again instantaneously, or After the destruction of oil facilities, the source of oil products is discharged and stable combustion takes place with sufficient air.
(2) Combustion causes explosion. During the combustion process, as the tank body is continuously heated by high-temperature baking, the oil in the container rapidly evaporates, forming an explosive gas mixture and exploding in the event of an open flame, or bursting due to the container cannot withstand the expansion pressure of the internal oil vapor. Then it exploded.
(3) Explosion cycle. No matter whether it is after the first explosion or after the first explosion, the oil depot fire does not end in only one cycle. Instead, the oil reserves, the spread of fire, and the security situation continue to develop, and the combustion and explosion transform each other, further threatening the surrounding storage. Oil products.
2, violent fire, strong heat radiation
The fire load of petroleum products is large, and the high temperature of the fire will occur after the fire. 1 kg of high quality gasoline complete combustion 90, the releasable 10400-11250 kcal / kg of heat, with a capacity of 200 m3 tank if fire, the flame temperature can reach 2000 ℃. Thermal radiation from the combustion of oil can easily cause combustion or explosion near the tank.
3, the formation of stable combustion
If the leakage of oil or less volatile oil vapor, or the amount of air in the container is small, the concentration of air mixed with the air can not reach the upper and lower limits of the explosion limit, the failure to meet the open fire or spark with ignition energy The explosion only forms stable combustion, and the combustion may continue until the oil burns out without exploding.
In addition, there will be explosions but no combustion.
Second, the difficulty of oil depot fire disposal
1. The risk of explosion and poisoning is high. Leakage of petrochemical equipment can easily lead to chain-lock reactions such as explosions and combustion, and there are dangers such as high temperature, explosion, collapse, poisoning, re-explosion, and rogue fire, which pose a threat to firefighters' operations.
2 , rapid development, easy to form a three-dimensional fire. The petrochemical equipment process is miscellaneous, there are many circulating materials, the reaction conditions are harsh, and the equipment pipelines criss-cross. The explosive leakage of the fire points occurs. It is easy to form three-dimensional combustion. The heat value is high and the radiation is strong. It is difficult to implement close-in firefighting.
3 , high technical requirements for process disposal. The production process is complicated, and the implementation of process disposal needs to be implemented by the technical personnel of the unit according to the site conditions.
4 , fire protection requirements are high. After the device is exploded by fire, damage to the fixed fire-fighting facilities will not be effective. It is necessary to call mobile equipment to perform long-term cooling and the demand for water supply is large. The material composition of the device is complex and the state is varied. It is necessary to reasonably select fire extinguishing agents such as water, dry powder, and foam.
5. Organizational coordination is difficult. The noise at the disposal site is large, and there are many forces involved in the operation. It involves many units and departments, communication and communication difficulties, and demand for coordinated action.
Third, large-flow, high-intensity foam + water coordination
The types of fires in the oil depot are various and the fire extinguishing methods are not the same. In an interview with this publication, the Shanghai Yangpu Fire Brigade suggested that according to the characteristics of the fire, based on the conventional fire extinguishing methods, flexible methods should be adopted to effectively extinguish the oil depot fire.
1. Stable burning tank fire
Tank fire may occur at the hole of the tank. For example, in the cracked gap, a stable torch-type combustion is formed at the breathing valve, the oil hole, and the light hole. At this time, the water flow closure method and the cover method may be used for extinguishing the fire. The flow closure method is based on the size and height of the torch diameter, organizes several shooting groups, and aligns the flame roots from different angles. The water flow separates the flame from the unburned oil vapor, causing the interruption of the supply of instantaneous combustible gas and the extinguishing of the flame. Covering a fire is to cover the flame with a cover (wet quilt, sacks, asbestos, etc.), causing an instantaneous barrier between oil and gas and air, causing the flame to extinguish.
2. Oil spill fire
First of all, it is necessary to organize the rescue of the dispersed liquid flame in the embankment, and then rescue the fire in the tank. When there is a large burning area in the fire protection dyke, fire fighting tactics shall be adopted to block and enclose, and enough foam tube guns or foam guns shall be concentrated and arranged outside the fire dyke to fully surround the combustion area. First use dry powder fire extinguishing agent to control the flame, then use fluorinated protein foam to start spraying foam from the edge of the fire bank, and gradually move to the center of the fire bank to cover the combustion liquid surface.
3, boiling oil tank fire
After a fire has occurred in a boiling oil tank, it is necessary to concentrate on cooling the combustion tank or draining water from the tank to prevent boil over before boiling overflow occurs. For a fire that has experienced oil boiling, a method of embankment should be adopted to prevent the oil from flowing to the surrounding area without restrictions and to control the combustion within a certain range. For the combustion oil in the encircled area, it is necessary to take a tampering and enveloping, and from different directions, tap into the combined attack and shrink the encirclement to create conditions for the fire outside the tank. From the above description, it can be seen that when fighting an oil depot fire, two strategies are crucial: large flow, long-range foam and water, and cooling.
At present, air-fighting fire extinguishing systems are often used for fighting tank fires. The air bubble has a suffocating effect on the fire. After a certain thickness of foam covers the oil surface, the oxygen content in the combustion zone will decrease and the fire will gradually weaken until it is extinguished. At the same time, the air foam also has heat insulation, which effectively reduces the heat radiation from the flame to the oil surface, reduces the oil surface temperature, and reduces the evaporation of the oil. Since the main component of the air foam film is water, it evaporates and vaporizes when heated and absorbs a lot of water. The heat can also cool and cool the tank.
Cooling this step is crucial to prevent oil tank explosions and fires from spreading and bring unnecessary losses to fire fighting. Therefore, the fire department recommends using high-dose foam or water to cool the fire tanks and the adjacent tanks and extinguish the ground oil fire. , and then save the cupping. When a certain effect is achieved on the cooling of the cupping tank and the adjacent tank, the foam can be used to extinguish the cupping tank when the fire fighting battle is performed.
Finally, it should also be noted that when fighting a tank fire, do not fight water and foam in each tank. Otherwise, water and foam injected will lead to premature boiling and splashing.
Fourth, pay attention to matters
According to information provided by the Zhenhai Fire Brigade, the basic tactics for fighting a tank fire are:
1. Start fire cupping, adjacent tank cooling, fire extinguishing device, cooling and fire extinguishing
At this point, the fire pump should be pressurized water supply to the water supply line, and turn on the foam pump, adjust the proportion of foam liquid, pressurize the foam line to supply the foam mixture.
2. Rapidly extinguish the flow of fire and continuously cool the oil tank to prevent the tank temperature from increasing sharply.
After a period of combustion, after oil spills form a large area of ​​turbulent fire, foam shall be used in a fixed foam fire extinguishing device in the reservoir area, and fire fighting water tanks shall be erected in the reservoir area to continuously cool the tank body.
3 , strengthen the cooling power, strong cooling of the oil tank
After the extinguishing of the streamer fire, the tank burns fiercely, the temperature of the tank body and the oil surface is high, and the heat radiation is strong. At this time, all the power should be strongly cooled to reduce the temperature of the tank body and the liquid surface to prevent explosion and ensure stable combustion.
4 , Concentrate on the total fire extinguishing, after the fire is extinguished, continue cooling
5. During the fire fighting process, pay attention to the following points:
1. The devices and facilities for cooling the surrounding surface of the bonfire shall be sprayed with foam from the device to prevent re-ignition due to cooling water flowing down and destroying the foam cover on the ground.
2. During the process of plugging and transmission after extinguishing the fire, it is necessary to prevent re-combustion and re-explosion of leaked materials due to improper protection of water mist.
3 , long-term operations or night, hot, cold conditions, to prepare enough reserve forces to replace first-line combat personnel. For vehicles and equipment that continue to work, attention should be paid to supplementing oil and promptly organizing replacement maintenance.
4. For the petrochemical plants with higher integration procedures, prior to the implementation of technical measures such as shutting off the valve, stopping the device, and so on, the unit must be required to perform system safety disposal demonstration assessment to prevent new dangerous situations due to the system correlation between the devices.
5 , as soon as possible to put foam fire extinguishing, prevent the oil temperature is too high, reduce the effect of foam fire
Prior to the application of foam to the tank, the mixing ratio of the foam should be checked. Only when it is normal, can the fire be effectively extinguished. The foam should be discharged under the unified order to prevent the oil spillage caused by excessive application and the formation of the streamer fire.
6 , the fire tank, adjacent tank cooling throughout the entire fire extinguishing process
7. The use of fire fighting should be rapid, all foam gun positions should be fire-extinguished at any time, exiled as soon as possible, and do their best to control the temperature of the tank.
8. The tank cannot extinguish the tank fire when the tank is over 600 °C due to the influence of the flow fire . In this case, the cooling of the tank should be strengthened.
9 , cooling water gun (gun) should be in the tank wall along the lateral cooling, let the water flow from top to bottom cooling, cooling water flow as far as possible not to leave blank spots, uniform cooling tank wall
10. After the tank fire is extinguished, continue to cover it with foam and use a water gun to cool it.
The information in this article comes from the Internet and was reorganized and edited by China Rescue Equipment Network.
Thermostatic Radiator Valve Head
Thermostatic Radiator Valve Head
Ningbo Safewell Plumbing Co., Ltd. , https://www.safewellbrass.com