What are the hazards of an explosion in a chemical warehouse in Jiangsu, the collapse of an oil tank and the chemical explosion?

At 9 o'clock this morning, an explosion occurred in the warehouse of a chemical plant in Jingjiang, Jiangsu. It is reported that there are fuel tanks, diesel tanks, gasoline tanks and chemical storage tanks in this warehouse. At present, the fire continues. Look at the details again!

What are the hazards of chemical explosion caused by burning oil tanks in a chemical warehouse in Jiangsu?

At about 9: 40 am, a fire broke out in an exchange pump room of Jiangsu Deqiao Storage Co., Ltd. located in Jingjiang Xingang Park. The government launched the emergency plan at the first time. The Standing Committee of the Municipal Party Committee and the Secretary of the Municipal Party Committee gave instructions at the first time: make every effort to rescue the people scientifically, evacuate the people at the first time, ensure that there are no casualties, ensure that no secondary disasters occur, and ensure that the surrounding life and production order are not affected. Zhao Ye, deputy secretary of Jingjiang Municipal Committee and mayor, also rushed to the scene to direct the disposal.

At present, the fire has been effectively controlled and there are no casualties. After investigation and arrangement, the fire point has been determined and all connections with the fire source have been cut off. At the same time, the local safety supervision, environmental protection, water conservancy, port and other departments have monitored and evaluated the surrounding environment, and there is no abnormality, and the living and production order of the surrounding people is normal.

What are the hazards of chemical explosion?

1. Danger of chemical combustion and explosion

(1) explosion limit

Combustible gas, flammable liquid vapor or the mixture of combustible dust and air can explode in a fixed concentration range, but not in any mixing ratio. Different combustible substances have different fixed concentration ranges. This fixed range is usually called the explosion range or explosion limit of substances, and is usually expressed by the volume percentage of combustible gas, combustible liquid vapor and combustible dust in the air. The lowest concentration that can cause explosion is called the lower explosion limit and the highest concentration is the upper explosion limit. For example, the explosion range of ethanol is 4.3% ~ 19.0%. 4.3% is called the lower explosion limit and 19.0% is called the upper explosion limit. The explosion limit of gasoline is1.0% ~ 6.0%; The explosion limit of natural gas is 4.8% ~13.46%; The explosion limit of hydrogen is 4.0% ~ 75%; The limit value of carbon monoxide is12.5% ~ 74.2%; The explosion limit of ammonia gas is 15.5% ~ 27% and so on. The wider the explosion limit, the lower the explosion limit and the greater the explosion risk. The explosion limit is measured under standard conditions such as normal temperature and pressure, and this range changes with the change of temperature and pressure.

(2) Minimum ignition energy

The minimum ignition energy refers to the minimum energy required to cause the combustion and explosion of explosive mixture. For example, the minimum ignition energy of hydrogen is 0.0 19mJ, methane is 0.25mJ, ethane is 0.25mJ, ethylene oxide is 0.065mJ, and ethylene is 0.096mj The smaller the minimum ignition energy, the easier it is to catch fire.

(3) Explosion pressure

The pressure produced by flammable gas, flammable liquid vapor, flammable dust and air mixture and explosives when ignited and exploded in a closed container is called explosion pressure. The maximum explosion pressure is called the maximum explosion pressure. The explosion pressure is usually measured, but it can also be calculated according to the combustion reaction equation or the internal energy of gas. Different substances have different explosion pressures. Even for the same substance, the explosion pressure is different because of the different surrounding environment, original pressure and temperature. The higher the maximum explosion pressure, the shorter the maximum explosion pressure time and the faster the maximum explosion pressure rises, indicating that the greater the explosion power, the more dangerous the mixture or chemicals are.

2. Flammable or combustible liquid explosion hazard

(1) flash point and flash point

When liquid burns, under the action of ignition source, the liquid first evaporates into vapor, and then the vapor is oxidized and decomposed for combustion. On the surface of each liquid, there is a certain amount of steam. With the increase of liquid temperature, the vapor concentration also increases. When the steam concentration is higher than the lower explosion limit, it will burn when it meets the flame. At a certain temperature, when the mixture of saturated steam and air of combustible liquid comes into contact with the flame, it can produce sparks and burn instantly, which is called flash combustion. The temperature that causes the flash point is called the flash point. When the temperature of combustible liquid is higher than its flash point, there is always the danger of being ignited by flame. The lower the flash point, the easier it is for this chemical to cause combustion and explosion.

(2) Ignition point

In the case of sufficient air, a combustible substance will catch fire when it comes into contact with a flame (flame or cold light) at a certain temperature, and the lowest temperature that can continue to burn after moving to the flame is called the ignition point or ignition point of the substance.

(3) Autoignition point

The lowest temperature at which combustible substances are heated in air or oxygen without flame, electric spark and other fire sources, which causes combustion, is called the auto-ignition point (or ignition temperature).

There are two situations of spontaneous combustion:

Self-ignition by heating: The temperature of combustible materials rises under the action of external heat source, reaching the self-ignition point and burning by itself.

Spontaneous combustion: the phenomenon that combustible substances generate heat through physical, chemical or biochemical processes without being affected by external heat sources, and then accumulate for a long time to reach the spontaneous combustion point of the substances and burn by themselves.

The reasons for natural heat generation of substances are decomposition heat (such as celluloid), oxidation heat (such as unsaturated oil), adsorption heat (such as activated carbon), polymerization heat (such as liquid hydrogen cyanide), fermentation heat (such as hay) and so on. Spontaneous combustion is a common phenomenon in the storage and transportation of chemical products, which is extremely harmful.

3. Danger of solid combustion and explosion

Solid combustion can be divided into two situations. For simple substances, such as sulfur and phosphorus, they are melted first and then evaporated into steam for combustion, without decomposition process; For complex substances, they are first decomposed into their components when heated, resulting in gaseous and liquid products. Then, the gaseous and liquid products evaporate and catch fire.

The indexes for evaluating the combustion and explosion danger of solid materials mainly include ignition point, spontaneous combustion point, impact sensitivity, friction sensitivity, electrostatic spark sensitivity, flame sensitivity, shock wave sensitivity, maximum explosion pressure, maximum explosion pressure rising speed and so on. The lower the ignition point and spontaneous combustion point, the more flammable the solid matter is.

Impact sensitivity, friction sensitivity, electrostatic spark sensitivity, flame sensitivity and shock wave sensitivity are important indexes to evaluate the explosion risk of chemicals, which refer to the sensitivity of articles to impact, friction, electrostatic spark, flame, shock wave and other factors respectively. For example, organic peroxides are very sensitive to impact and friction. When it is subjected to external impact or friction, it is easy to cause articles to burn and explode. Therefore, when handling organic peroxides, we should handle them with care and avoid falling, touching, dragging, pulling, falling and throwing. After the oxidized solid comes into contact with the reduced solid, it reacts violently, releases heat, and even burns with the participation of moisture in the atmosphere. Therefore, it is exaggerated that hazardous chemicals should be classified and stored.

4. Damage caused by fire and explosion.

Both fire and explosion will cause great damage to production facilities and casualties, but their development processes are obviously different. After the fire broke out, it gradually spread and expanded. With the passage of time, the number of losses increases rapidly, and the loss is roughly proportional to the square of time. If the fire time is doubled, the loss may increase fourfold. The explosion is unpredictable. The explosion process may end in just one second, and huge losses such as equipment damage, factory collapse and casualties will also occur in an instant.

Explosion is usually accompanied by heat, light, pressure rise, vacuum and ionization, which has great destructive effect. It is related to the quantity and nature of explosives, explosion conditions and explosion locations. The main forms of damage are as follows:

(1) direct damage

Many devices, devices, containers, etc. It will be produced after the explosion, and it will cause damage in a considerable range after flying out. Generally, debris is scattered in the range of 100 ~ 500m.

(2) the destructive effect of shock wave

When a substance explodes, the generated high-temperature and high-pressure gas expands at a very high speed, squeezing the surrounding air like a piston, and transferring part of the energy released by the explosion reaction to the compressed air layer. Air is disturbed by impact, which makes its pressure, density, etc. A sudden change. This kind of disturbance propagating in the air is called shock wave. The speed of the shock wave is extremely fast. In the process of transmission, it will destroy the mechanical equipment and buildings in the surrounding environment, causing casualties. Shock wave can also produce vibration in its action area, making objects loose or even destroyed by vibration.

The damage of shock wave is mainly caused by overpressure on its wave front. Around the explosion center, the overpressure on the air shock wave front can reach several or even more than ten atmospheres. Under such high overpressure, buildings will be destroyed and mechanical equipment and pipelines will be seriously damaged.

When the shock wave acts on buildings in a large area, the overpressure of the wave front is within 20kPa~30kPa, which is enough to destroy most brick and wood structures. When the overpressure exceeds 100kPa, all buildings will be completely destroyed except the solid reinforced concrete buildings.

(3) causing a fire

After the explosion, the diffusion of explosive gas products only takes place in a very short time. For ordinary combustible materials, it is not enough to cause fire, and the explosion wind caused by shock wave can also put out the fire. However, the high temperature and high pressure generated by the explosion will leave a lot of heat or residual flame in the building, which will ignite flammable gas, flammable or flammable liquid vapor flowing out of the damaged equipment, and may also ignite other flammable substances to cause a fire.

When flammable containers and pipes in colorful clothes explode, the flammable substances thrown out by the explosion may cause a large-scale fire, which is most likely to happen after the explosion of oil tanks and liquefied gas cylinders. Combustion equipment or high-temperature chemical equipment in operation is damaged, and its thermal debris may fly out; Igniting fuel or other combustible materials stored around can also cause fire.