In recent years, chemical explosions have occurred frequently. The injured people and the lost money are even more distressing. Let us review the more serious chemical explosions that have occurred in recent years:
"8·12" Tianjin chemical explosion, two loud and loud noises, four fires, black smoke all over the sky, heavy casualties for only over the years, more affecting the hearts of Chinese people.
On April 16, 1947, the "Grand Camp" cargo ship was loaded in the US port of Texas, and a big bang occurred on the spot. There are many loopholes in the transportation and management of chemicals in the United States, and there is almost no defense against explosions in high temperature environments. At 8 o'clock in the morning, 2,100 tons of warehouses were smoked and the flames burst out. The fire brigade was busy spraying water on the ship, but the hull was hot enough to evaporate the water directly.
On September 21, 2001, the Toulouse chemical plant AZF exploded, and a large pit of more than 50 meters wide and 15 meters deep was blown. Two factories were leveled, 31 people were killed and 2,500 people were injured. The explosion seismic wave is equivalent to a magnitude 3.4 earthquake. The surrounding 30,000 sets of houses within a radius of 6 kilometers and hundreds of companies suffered heavy losses, with a loss of 2.3 billion euros. The investigation found that a few kilograms of sodium dichloroisocyanate was mixed with the ground on the ground before a quarter of an explosion, causing a strong explosion of 300 tons.
After 14 years of bombing, the entire AZF factory was completely decontaminated, and a cancer research center was built on the factory site. The insurance company paid 2 billion euros... but the questioning has not stopped.
Today, Shanghai Hengyuan Biotechnology Co., Ltd. introduces how various chemicals are fireproof and explosion-proof: a) Fire and explosion of gaseous hazardous chemicals The dangers of fire and explosion of chemicals are mainly from those that exist in a gaseous state at normal temperature.
Flammable gas
.
Flammable gas
It refers to gases that can burn or explode when exposed to fire, heat or contact with oxidants in the air, such as oxygen, acetylene gas, petroleum liquefied gas, and city gas.
Fire characteristics and dangerous properties of gaseous hazardous chemicals (1)Flammable gas
The difference between burning and burning of liquids and solid materials.
1 Liquids and solid materials that are easily ignited by burning must undergo evaporation, melting, etc., in order to burn under gaseous conditions, and the gas already has combustion conditions at normal temperature, and only needs to provide oxidizing or decomposing gaseous substances and heating them to the ignition point. The heat causes combustion, so the gas is more likely to ignite than liquids and solids.
2 gas combustion has two forms: one is stable combustion, also known asDiffusion combustion
One is explosive combustion, also known as power combustion. If the mixing of the flammable gas and the combustion-supporting gas is carried out during the combustion process, stable combustion occurs. For example, a gas-fired welding torch is a stable combustion formed by the action of gas diffusion. At this time, the mixing of the combustible gas and the oxygen is carried out during the combustion process, and as long as the control is good, no fire will occur. If the mixing of flammable gas and combustion-supporting gas is carried out before combustion, and the concentration of the mixed gas is within its explosion range (ie
Lower explosion limit
with
Upper explosion limit
Between the two, in the event of a fire source, explosive combustion occurs. Side of the coal mine
Gas explosion
This is the case.
(2) Other dangerous properties of flammable gases.
1 Chemical activity: Gases with unsaturated bonds in the molecular structure are chemically active. Under normal circumstances, some gases will chemically react upon contact with each other to cause a combustion explosion. For example, acetylene will explode when exposed to chlorine or fluorine. In general, the more unsaturated bonds in the molecular structure, the greater the risk of fire and explosion.
2 diffusibility: flammable gas that is slightly lighter than air escapes in the air, and most of it diffuses upwards, drifts in the wind, and is less likely to accumulate. Flammable gas that is heavier than air, especiallyLiquefied gas
When leaking out, it often floats along the ground and spreads to a farther place or gathers in the ditch and the corner of the building. It will not gather for a long time. When it encounters a fire source, it will spread the flame and a large area will occur. Burning or exploding.
3 Corrosive: Some flammable gases are corrosive. For example, hydrogen sulfide, ammonia, etc. can corrode equipment, reduce the pressure resistance of the equipment, and in serious cases, the equipment may leak, causing fire explosion and poisoning.
4 Chargeability: Compressed or liquefied flammable gas can generate static electricity when it is ejected at high speed from the nozzle or break. The main reason is that the gas contains solid particles or mist impurities, and when it is ejected at a high speed, it is strongly rubbed against the nozzle to generate static electricity. The more solid or liquid impurities contained in the gas, the stronger the static generated. If the equipment is made of insulating material, or made of metal material, but not well grounded, the static electricity will be concentrated into a high voltage, and the electric spark generated by high-voltage electrostatic discharge can ignite flammable gas (such as hydrogen) and A mixture of air causes an explosion.
5 Toxicity: Some flammable gases are toxic, and special care should be taken to prevent poisoning during transportation, storage and use.
Fire and explosion protection measures for gaseous hazardous chemicals (1) Control of heat source (ignition source). The flammable gas can directly participate in the combustion, so controlling the heat source (ignition source) is the most basic measure to prevent the flammable gas from igniting. In places where flammable gases are produced, used, and stored, fire must be prohibited except for the use of fire.
(2) Leak check. In large and medium-sized places where flammable gas is produced, used and stored, a flammable gas monitoring type leak detection alarm device shall be provided. When the concentration of flammable gas in the air exceeds the gasLower explosion limit
When the concentration is 25%, it can automatically alarm. At the same time, a portable leak detector should be equipped for patrol monitoring.
Many flammable gases are colorless and odorless. In order to increase the chance of leak detection, some of the more widely used fuel gases are usually "smelted". For example, a small amount of organic sulfur compounds is added to general fuel gas, natural gas, and liquefied petroleum gas, and a slight scent can smell a pungent smell.
(3) Safety management and measures for gas cylinders.
(2) Fire hazard of liquid hazardous chemicals The fire and explosion hazard of liquid hazardous chemicals mainly comes fromFlammable liquids
Most of these substances are organic compounds. Many of them belong to
Petrochemical
The product is easy to catch fire at room temperature.
Flammable liquids
The dangerous trait (1) is highly flammable.
Flammable liquids
Very easy to burn, the main reasons are:
1 Because the flammable liquid has a low flash point, its ignition point is also low (the ignition point is generally higher than the flash point by about 15 ° C), so the contact fire source is easy to catch fire and continue to burn.
2 Most flammable liquids are organic compounds, and the carbon content in the molecular compositionYuhe
Oxygen atom. It is easy to react with oxygen and burn.
3 Most flammable liquids have small molecular weight, low boiling point and are easy to volatilize. The vapor pressure is large. Due to the high volatility, the vapor concentration of these liquid liquids is also large, and it is easy to catch fire when exposed to fire or sparks.
4 The flammable liquid requires very little energy to ignite, and only requires a very small energy spark to ignite.
5 Vapor of flammable liquids is generally heavier than air, and it is easy to deposit in low-lying or underground rooms. It does not scatter for a long time, which increases the risk of fire.
(2) Flammable liquids are highly volatile. When the volatilized volatilized vapour is mixed with air and its concentration is between the explosive range of the flammable liquid, it may cause an explosion if it is exposed to an open flame or a spark. The bigger the explosion, the bigger theLower explosion limit
The lower the flammable liquid, the greater the risk.
(3) Highly mobile diffusible flammable liquids are generally very small in viscosity. These substances are not only very easy to flow, but also due to penetration, infiltration and capillary phenomena. Even if the container has only very fine cracks, the flammable liquid will seep out of the container wall, enlarge its surface area, and continuously evaporate. The concentration of flammable vapor in the air increases, thereby increasing the risk of fire and explosion.
(4) The expansion coefficient of flammable liquid is relatively large. After being heated, the volume is easy to expand, and the vapor pressure thereof is also increased, so that the internal pressure of the sealed container is increased, causing a "drum" or even a burst. At this point, if there is a spark (a spark may also be generated when the container bursts), it will cause a combustion explosion.
(5) Some flammable liquids are in contact with oxidants or oxidizing acids (especially nitric acid), which can cause violent reactions and cause fire and explosion. This is because the flammable liquid is organic, easily oxidized, and can react with the oxidant to generate a large amount of heat, causing the temperature to rise to the ignition point and causing a fire explosion. For example, when turpentine encounters concentrated nitric acid, it will burn immediately.
Fireproof and explosion-proof measures for liquid hazardous chemicals (1) The warehouse for the use and storage of flammable liquids shall be a first- and second-class refractory building. It is required to be well ventilated, and fireworks are strictly prohibited around it, away from fire, heat, oxidants and acids. In the summer, heat insulation and cooling measures should be taken, and the low-boiling ether, carbon disulfide and petroleum ether should be taken for cooling and cooling.
(2) Where a flammable liquid is used or stored, the explosion-proof electrical appliance shall be selected according to the relevant regulations. It should be handled gently during loading and unloading and handling. It is strictly prohibited to carry out safety operations such as rolling, friction and dragging. It is forbidden to use iron tools that are prone to sparks and shoes with nails on the feet during work.
(3) When filling the flammable liquid, there should be more than 5% of the gap in the container, which should not be filled to prevent the burning or explosion of the flammable liquid from thermal expansion.
(4) It must not be mixed with other dangerous chemicals. Dangerous goods cabinets may be installed in the laboratory. A small amount of bottled flammable liquids used in the laboratory shall be stored according to the nature. The solids shall be placed on the upper grid and the liquid shall be placed in the lower grid; the oxidant, reducing agent and other properties shall not be mixed in the same grid. Conflicting items (mixed danger).
(5) Most vapors of flammable liquids have certain toxicity and will invade the human body from the respiratory tract and cause harm. Special attention should be paid to the integrity of the packaging of flammable liquids.
(3) Fire-retardant solid-state hazardous chemicals for solid hazardous chemicals (excluding substances already listed in explosives) are usually defined as: violent chemical reactions that can be caused by heat, friction, impact or contact with oxidants, which can cause combustion and dust Explosive solid chemicals. According to its different combustion conditions, it is divided into flammable solids, spontaneous combustion items, and wet and flammable items. In addition, in the classification of oxidants and organic peroxides, most of the goods are solid hazardous chemicals. All of the above knowledge should be mastered and helpful to everyone. If you have any questions, please feel free to contact us and we will answer your questions.
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