Prevention and fighting measures for the most expl

Explosive fire prevention and suppression measures

explosive fire prevention and suppression measures (LPG) -- Introduction (1)

LPG is a mixture of hydrocarbons such as propane, propylene, butane, butene, etc. as fuel and chemical raw materials, it is more and more widely used. Due to its flammable and explosive characteristics, it is very easy to cause fires in the process of production, storage, transportation and use, Even cause catastrophic explosion accidents. It is of great significance to strengthen the research on the prevention and suppression measures of LPG explosive fires

explosive fire prevention and suppression measures (LPG) -- explosion type (2)

(1) chemical explosion

LPG is usually stored in liquid form under normal temperature and pressure, which is very dangerous in case of leakage. When the storage tank breaks, 1m3 of liquefied petroleum gas can be converted into 250~300m3 of gaseous petroleum gas. The explosion limit of liquefied petroleum gas is calculated according to the approximate value of 2%~9%, then 1m3 of liquid liquefied petroleum gas will leak into the atmosphere and become 3000~15000m3 of explosive gas. The minimum ignition energy of LPG is 0.2~0.3mj, which is very easy to detonate. Gaseous LPG is heavier than air. After leakage, it is easy to diffuse along the ground and accumulate in low-lying places, so it is not easy to escape. The gas is colorless and tasteless, so it is not easy to be detected. Only when a large amount of gas is rapidly concentrated and distributed, white fog can be seen or spray sound can be heard. When explosion occurs in case of open fire, it has spread over a considerable area, and the chemical explosion of leaking LPG is often sudden

(2) physical explosion

the flash point of liquefied petroleum gas is lower than -60 ℃, which is flammable. When the storage tank or its accessories leak and catch fire, the storage tank itself and its adjacent tanks will be in a heated state. The form of flame acting on the storage tank includes that the fuel pool flame leaked to the ground partially or completely surrounds the container, and the spray flame or torch at the crack barbecue the tank wall or adjacent tank body. After the storage tank containing liquefied petroleum gas is heated, the temperature of the tank wall and its internal liquefied gas rises, and even the liquefied gas boils, raising the internal pressure. As the temperature of the shell in the gas phase above the liquid level rises rapidly, the strength of the metal vessel wall will decline. At the same time, there is a temperature difference at the gas-liquid interface, local thermal stress will be generated on the vessel wall, and the vessel wall will be stretched under the increased internal pressure, resulting in cracks. The high-pressure gas will be ejected through the opening, the pressure in the vessel will drop rapidly, the liquefied gas will be in an overheated state, and then evaporate instantly, resulting in a biological rational vapor explosion. The ejected materials are immediately ignited by the fire source, resulting in fireballs and strong thermal radiation. If it is not ignited immediately, the ejected liquefied gas will mix with the air to form a flammable gas cloud, and a secondary chemical explosion will occur in case of an adjacent fire source

(3) explosion hazard characteristics

the explosive gas formed by the leakage of liquefied petroleum gas will cause chemical explosion when encountering the fire source, and its explosion power is large. The explosive power of 1kg liquefied petroleum gas is about equal to the equivalent of 4~10kg TNT explosive, and the explosive speed can reach 2000~3000m/s. Due to the large calorific value of liquefied petroleum gas, the calorific value of 1m3 is 6 times that of coal gas, and the flame temperature is as high as 1800. Cotton is high purity (98%) cellulose ℃. Therefore, after the explosion and fire of liquefied petroleum gas, it will quickly ignite all combustibles in the explosion area, form large-area combustion, and cause major damage and casualties. The chemical explosion of the tank is more destructive than the physical explosion

physical explosion of liquefied petroleum gas tank, also known as vapor explosion, is also very destructive. Its main hazard factors are fireball, shock wave and projectile. When the storage tank breaks down, most of the liquefied petroleum gas ejected is mixed with the surrounding air in the form of fog droplets and ignited. The high-temperature thermal radiation hazards and duration of the fireball are related to its size. The larger the amount of liquefied petroleum gas loaded in the storage tank, the more the amount of steam explosion and combustion, the larger the radius of the fireball formed, the longer the duration of the fireball, and the greater the degree of thermal radiation damage around. With the increase of distance, the thermal radiation of the object by the fireball will continue to decrease. The radius of the fireball, the duration of the fireball, and the relationship between the thermal radiation flux of the object by the fireball and the distance can be estimated by equations (1), (2) and (3) respectively. The damage of shock wave is smaller than that of fireballs and projectiles. The peak overpressure of shock wave is greater than 0.003mpa, which will cause obvious damage. Projectiles are the ones with the greatest impact distance of vapor explosion hazards. Explosive projectiles can fly tens of meters to 100 meters. The vapor explosion projectiles of storage tanks with small volume (0.4m3) are tightened in time, mostly within the radius of 3-6 fireballs. Among them, the auxiliary projectiles, such as the pipes on the tank, supporting legs, other accessories and other connectors or nearby objects, are subject to explosion, and the ejection distance of the projectiles generated by the shock wave is large under the greater downward pressure of the economy. If there are too many sundries accumulated near the tank, the harm of the auxiliary projectiles will be increased; For cylindrical horizontal storage tanks with large volume (0.4~130m3), 80% - 90% of the side projectiles are within 4 fireball radii, and more than 90% are within 5-7 fireball radii; Part of the violent tank can reach 14~22 fireball radii, and a few explosive projectiles can reach 30 fireball radii; Cylindrical horizontal storage tank has explosive projectiles in all directions, but the distance reached by the projectiles at both ends is farther than that at the side