Petrochemical fire and prevention

Petrochemical refers to the industry that uses petroleum and natural gas as raw materials to produce various petrochemical products through physical and chemical processing and mechanical processing. It involves all areas of the national economy, is an important industry that is indispensable to the national economy and the people's livelihood, and is one of the pillar industries of the national economy. It occupies a very important position in the national economy.

The petrochemical industry has a complicated production process and a wide variety of equipment. It is an industry with complex processes and strong technical capabilities. Since the raw materials, semi-finished products, finished products and various auxiliary materials used in the production process are mostly flammable and explosive substances, it is easy to cause fire and explosion accidents, and the fire is fierce and difficult to extinguish when it is on fire. Therefore, the petrochemical industry is also a fire explosion. It is dangerous, and in the event of a fire or explosion accident, the industry with large losses, high casualties and high impact has always been the focus of fire protection.

There are many influencing factors in the fire hazard in the petrochemical production process. Some people have operations and process conditions, as well as administrative management and technical business. From the perspective of fire protection, the factors that may cause fire and explosion accidents in the petrochemical production process can be summarized as follows:

1. Most of the raw materials, finished products and semi-finished products used in petrochemical production are inflammable and explosive. These items are prone to burning or explosion when they encounter fire sources, and the fire is fierce and the propagation speed is fast.

2. Most petrochemical production processes use high temperature, high pressure or cryogenic, negative pressure process conditions. High temperature, high pressure and deep cooling can improve single machine yield and product yield, so as to shorten the production cycle of the product and obtain the best economic benefit; negative pressure is conducive to the safe production of easy fuel. However, the unsafeness of materials and equipment brought about by high temperature and high pressure conditions is also obvious. It can increase the activity of materials, expand the range of explosion limits, and can cause deformation of equipment piping interface, causing material leakage; It is safe, but it may inhale air due to low airtightness of the equipment and form an explosive mixture with combustible materials. Low temperature cryogenic freezing may freeze certain water-containing materials, causing blockage or rupture of the pipeline. Fire and explosion accidents caused by the above reasons are harmful and have serious consequences.

3. The production mode of petrochemical industry has the characteristics of continuous and automatic. If there is a valve opening error, parameter out of control, component failure, blocked passage or interruption of operation in the production process, it will cause a chain reaction and cause devastating disaster.

4. The petrochemical production equipment and equipment are large-scale, three-dimensional and group-oriented. The furnaces, towers, tanks, pumps and vessels are tall and large, the layout is concentrated, and the pipelines are vertically and horizontally connected. Once a fire occurs, it will not only cause a chain reaction, but also involve the surface. Large, easy to form a three-dimensional fire, increase the difficulty of saving, resulting in serious losses.

5. There are many power sources for petrochemical production, and fire sources, power sources and heat sources are intertwined. If these power sources are improperly set or poorly managed, they can directly become the source of fire and explosion accidents.

These potential risk factors develop into catastrophic accidents when operating conditions change, processes are disturbed and abnormalities occur, or human factors cause misuse.

In the past 20 years, the world's petrochemical industry has developed rapidly, and major fires and explosions have been caused. For example, the continuation of oil accidents in oil complexes in Japan in 1973 and 1974 not only caused major casualties and property losses, but also seriously polluted the surrounding waters. In 1975, the American Union Carbide Company's Belgian company Antwerp plant produced an annual output of 150,000 tons of high-pressure polyethylene. The reactor was leaked due to a leak in the reactor lid, and a chain reaction occurred. The entire plant was destroyed. In 1978, the accident occurred in Spain due to over-loading and sun exposure, resulting in an explosion in the acrylic workshop, killing more than 200 people. In 1982, the oil storage tank of a large power plant near Caracas, the capital of Venezuela, exploded, killing 145 people and injuring more than 500 people. The heavy casualties were rare in the world oil storage tank fires.

China's petrochemical industry started in the 1960s, and currently has more than 100 large and medium-sized petrochemical enterprises, almost all over the country. Every year, the country supplies a large amount of petroleum products, synthetic fibers, plastics and fertilizers, as well as some basic chemical raw materials, which have made great contributions to the rapid development of China's national economy and the improvement of people's lives. At the same time, fires and explosions in the petrochemical industry have also occurred frequently, causing serious losses to the national property and the lives of the people. According to the statistics of China Petroleum and Chemical Corporation from 1983 to 1993, among the 1143 accidents, the fire and explosion accidents accounted for 23.64%, but the losses accounted for 40%, and some destroyed dozens or even hundreds. Equipment, some ruin the entire production unit or the entire plant. Caused the entire plant to stop production,

The lessons have been seriously affected by production and economic benefits.

For example, in August 1989, the oil storage tank of the Huangdao Oil Depot was triggered by a lightning strike, which caused a fire in the tank area and shocked the whole country. Li Peng, then Premier of the State Council, visited the site in person. The fire burned for 5 days and 4 nights before being extinguished, causing heavy economic losses. Only 80 firefighters were killed or injured, 12 fire engines were destroyed, and the oil leaked from the fire polluted the surrounding seas. The longest burning time, the large loss, and the number of casualties of firefighters are the first in our history. In June 1997, the storage tank area of ​​Beijing Dongfang Chemical Plant caused a fire and explosion accident due to the leakage of ethylene equipment. The tank area of ​​10 million m2 became a ruin, causing economic losses of over 100 million yuan. It can be seen that in the event of a fire and explosion accident in a petrochemical enterprise, it is not only a damage to the equipment, but the enterprise ceases production.

It will also bring serious economic losses and harmful consequences to the country and society.

Petrochemical fires are different from other fires. Due to the characteristics of the petrochemical industry itself, namely the fire hazard of production and use of materials, special production processes and special construction and structure, petrochemical fires have various forms of fire and explosion hazard. Severe, large fire damage, large impact, difficult fire fighting, and high cost of fire fighting.

1. More explosive fires

Explosion caused by fire or explosion in fire is a prominent feature of petrochemical enterprises. In petrochemical production, fires and explosions are two accidents of different nature, but the chain reaction and its causal relationship often occur simultaneously or continuously. Therefore, the two are often referred to as fire and explosion accidents.

Petrochemical companies are most common in explosive fires because most of the raw materials, intermediates and final products used in production are flammable and explosive; the equipment used in production is mostly pressure vessels, and Mostly sealed or sealed, if the temperature, overpressure or abnormal reaction occurs in the equipment due to operation and other reasons, the equipment will explode; plus the petrochemical enterprises are continuous production process, continuity Operation, each device in the process flow colludes with each other. Once a device explodes, it can easily spread to adjacent devices and cause a systematic chain explosion.

The explosion of petrochemical enterprises is prominently manifested in the explosion accidents that occurred during the operation of production equipment, which is very sudden and has a great threat to the casualties of personnel.
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2. Large area of ​​rogue fires

There are many flammable liquids in petrochemical production, and liquids have good flow characteristics. When the storage equipment is seriously damaged, the liquid will rush out quickly. If it is accompanied by fire, it will cause a large area of ​​rogue-like fire. situation. Large-scale rogue fires are likely to occur in tank areas where oil is stored or in barrels of oil storage, and there are cases where fires occur in production facilities that handle large amounts of flammable liquids. The rogue fire spreads rapidly. If it cannot be controlled in time, it will easily cause large-scale burning and equipment explosion accidents.

3. Three-dimensional fire

Because petrochemical enterprises have the flammable, explosive and rogue diffusion of materials, the three-dimensionality of production equipment and the holes in the building are numerous and colloidal. Therefore, once the initial fire control is unfavorable, the fire will expand rapidly. And a three-dimensional fire is formed. The three-dimensional fire is threatening to neighboring buildings, the fire spreads rapidly, and the fire is difficult to save.

4. The fire is developing fast

The production workshops and warehouses of petrochemical enterprises are places where the combustibles are extremely concentrated. Once they are on fire, their combustion intensity is high, the fire field temperature is high, and the radiant heat is strong. In addition, the rapid diffusion of combustible gas and the fluidity of liquids and the interoperability of buildings are conditions. The impact of the factors, its fire spreads faster. According to experimental data, the burning speed of fires in petrochemical enterprises is more than double that of ordinary building fires, and the temperature in burning zones is generally higher than 500 °C. The flame and heat transfer will not only make the fire equipment warm up quickly, but also heat adjacent equipment and combustible materials, causing explosion and ignition dangers, and the fire spread faster.

5. Large fire damage and large impact

The losses caused by petrochemical fires are greater than those of public or civil buildings. According to the results of fire statistics estimates, the average economic loss per fire is about 5 times higher than that of other manufacturers, and often every fire damage is high. Millions of fires. In addition to causing direct economic losses and casualties, the fires of petrochemical enterprises will also cause indirect losses caused by production suspension and repair, especially for enterprises that produce chemical raw materials and intermediate raw materials, and the suspension of production caused by fire often leads to related enterprises. Shutdown and waiting for materials will seriously lead to a shortage of products urgently needed by some societies, causing social imbalance between supply and demand.

6. It is difficult to extinguish fires, and the firepower is much more expensive.

The fire characteristics and fire field forms of petrochemical enterprises determine the difficulty of fire fighting and the consumption of firepower are different from ordinary fires. Petrochemical fires are difficult to control at the beginning, mostly in the form of large fires, or large-scale fires, or three-dimensional fires, or multiple fires. The fire is developing rapidly and violently. The explosion is extremely dangerous. The burning substances and products have many toxic side effects, and the fire is saved. The manpower and material resources are many, and the technical requirements for the rescue are far from comparable to the general fire.
Therefore, it is not only necessary to do a good job in fire safety work in the petrochemical industry to prevent or reduce the occurrence of fire and explosion accidents. It is also very active in protecting the property and life of the country and the people, maintaining social stability and promoting the healthy development of the entire industry. The role.

The main measures to effectively avoid or prevent petrochemical enterprises from preventing fire and explosion accidents are as follows:

1. Control and eliminate fire sources

In the process of petrochemical production, there are many factors that cause fire and explosion, and the surface involved is also very wide. To prevent the occurrence of fire or explosion accidents, the first thing is to strengthen the control of the fire source to prevent the formation of a combustion explosion with combustibles and combustion-supporting materials. The system eliminates and strictly controls all sources of ignition that are sufficient to cause a fire.

The main sources of fire and explosion are open flames, high heat and high temperature surfaces, friction and collision, adiabatic compression, self-heating, electrical sparks, static sparks, lightning strikes and light and heat rays.
(1) Open flames, including smoking and the control of open flames in production. It is well known that smoking causes fires. The burning temperature of cigarettes is 650-800 °C when smoking, and the temperature is 450-500 °C during spontaneous combustion, and it can burn for a long time. Time, therefore, smoking should be prohibited in places where there is a risk of fire and explosion.

The open flame in production mainly refers to the heating fire in the production process, the maintenance of welding and cutting fire and other fire sources. To strictly control the use of open flame in production, for example, when heating flammable and explosive materials, avoid the use of open flame equipment; the arrangement of open fire heating equipment should be kept away from process equipment and storage tank areas that may leak flammable gases or vapors; When using fire, you should not use ordinary electric lights, candles, etc. in fire and explosion hazardous areas. Explosion-proof lighting equipment must be used. Mars extinguishing devices should be installed on the exhaust pipes of motor vehicles entering the factory and tank areas. Battery vehicles should be strictly prohibited from entering flammable. Explosive areas, etc.

(2) Control of high heat and high temperature surface

High-heat materials generally refer to objects with higher temperatures that can transfer heat to combustibles in a certain environment and can cause flammable substances to catch fire. Among the high-temperature and high-temperature surfaces are: high-temperature steam pipe surface, high-temperature gas, liquid pipe and metal surface of heat exchanger, heating furnace, drying furnace wall, cracking furnace, heating kettle, boiling hot pot, etc. Its surface. The temperature is high, the volume is large, and the heat is dissipated, which may become the ignition source of the combustion explosion. Effective insulation measures should be taken to prevent contact with flammable materials and to prevent combustibles and their dust from falling on them.

(3) Control of spontaneous combustion and chemical reaction heat

The substances which can spontaneously generate heat or generate chemical reaction heat include substances which generate heat due to oxidation reaction, such as oil immersion, coal, yellow phosphorus, metal powder, etc.; substances which generate heat due to decomposition reaction, such as nitrocellulose of nitrocellulose; Celluloid, gunpowder, etc. and some chemicals, such as perchlorate, chlorate, nitrate, permanganate and other inorganic peroxides, organic peroxides, alkali metal peroxides, etc.; fermentation caused by fever Substances and water-inhibiting substances, such as concentrated sulfuric acid, concentrated nitric acid, etc. These items should be kept and used in strict accordance with their respective physical and chemical properties and safety regulations.

(4) Control of impact and friction

When two hard surfaces with rough surfaces are violently impacted or rubbed against each other, they are prone to sparks. The thermal energy of this spark exceeds the minimum ignition energy of most combustible materials, enough to ignite combustible gases, vapors and dust. Such as the impact of flying objects, the impact of falling objects, the impact of pipes and equipment when rupturing, the impact of equipment damage and the friction caused by the vibration of towers, tubes and grooves, the friction of rotating parts such as bearings in machinery, and Impacts such as hammers, wrenches, etc., friction and impact between equipment, may cause sparks that cause fire and explosion. Strengthen the daily maintenance and management of the equipment; maintain good lubrication of the rotating parts of the machinery to reduce friction; use copper tools in dangerous places to effectively prevent friction and impact sparks.

(5) Control of adiabatic compression

Adiabatic compression of the gas causes the temperature to rise, causing the combustible to ignite or explode. Liquids with high explosive sensitivities such as nitroglycerin, nitroglycerin, and nitrates, as well as substances with low ignition points such as carbon disulfide, are prone to fire and explosion during adiabatic compression.

The most fundamental way to prevent adiabatic compression from becoming an ignition source is to avoid or control the conditions of adiabatic compression. For example, the speed of action should be slow when opening and closing the valve, minimize the occurrence of compressed flow, control the flow rate of fluid in the pipeline, and adiabatic compression process. The operation should be carried out after the discharge of various types of bubbles in the material.

(6) Control of electrical sparks

Fire and explosion accidents caused by electrical equipment are mostly caused by arc, electric spark, electric heat, electric leakage or short circuit. Whether the spark can constitute a fire hazard depends mainly on the spark energy, ie the ignition current, voltage and time of action; the breaking inductance; the size and shape of the arc or spark, and the chemical nature of the material mixture and its minimum ignition energy. The control of electrical sparks is mainly to take explosion-proof measures on electrical equipment. Such as the use of explosion-proof equipment, compartmental isolation installation, equipment to be reliably grounded and so on.

(7) Control of static sparks and lightning. In the production of petrochemical enterprises, there are many reasons for the generation of static electricity, such as liquid jet charging, liquid settling and charging, liquid conveying and charging. However, it cannot be said that there is a fire hazard when static electricity is generated. It is easy to cause electrostatic discharge only when the accumulated static electricity is large enough or the charged amount of the object is large enough and the electrostatic potential is high enough. If the spark energy of the discharge is greater than the minimum ignition energy of the material, a fire explosion may occur. The basic methods for preventing and eliminating static electricity are mainly considered from the following three aspects: first, to minimize the generation of static electricity; and second, to accelerate the leakage of static electricity and prevent static electricity accumulation in the case where static electricity is inevitably generated; In the case where a large amount of static electricity is generated and accumulated, measures to prevent discharge and fire are taken to reduce the amount of combustible materials so that they do not cause fire and explosion accidents.
Lightning is a discharge phenomenon of thunderclouds in the sky. When thundercloud discharges ground buildings (or objects), the lightning current can reach tens to hundreds of kA, so that a large current, even if the duration is short, can generate a large amount of heat on the discharge channel, and the temperature can reach several 10,000 ° C, can cause the factory to catch fire, causing flammable, flammable materials to explode and cause fire, as mentioned above, the Huangdao oil depot fire is caused by lightning hitting the oil storage tank. Therefore, petrochemical enterprises must take effective measures to prevent and reduce lightning. Lightning protection methods usually include lightning protection devices such as lightning rods, lightning protection lines, lightning protection nets, lightning protection belts, and lightning arresters. Lightning rods are mainly used to protect open-air power distribution equipment and protect buildings, structures, tanks and towers. The lightning protection line is mainly used to protect the power line.

Lightning protection nets and lightning protection belts are mainly used to protect buildings. Lightning arresters are used to protect electrical equipment and the like.

(8) Control of light and radiation

Ultraviolet light with a wavelength of less than 380 nm and infrared light with a wavelength of more than 770 nm have a high thermal effect and promote the chemical reaction, which can cause some unstable substances to catch fire or explode. Therefore, for the petrochemical raw materials and products in storage and transportation, effective light-shielding measures should be taken, insulation and heat insulation, and the influence of radiant heat should be weakened. Radiation is a high-speed particle beam or electromagnetic wave emitted when a radioactive element decays. It can ionize the gas, promote chemical reaction and release heat, and may cause fire. It should be "sealed" and "shielded" to prevent it. have an accident.

2. Chemical hazardous materials treatment

(1) Take fire and explosion prevention measures according to the physical and chemical properties of the substance

during production. It is necessary to understand the physical and chemical properties of various substances, and according to different properties, take corresponding measures to prevent fire and explosion and prevent the spread of disasters. In this regard, the first thing to consider is to replace the material with high risk of fire and explosion with a small dangerous substance through the improvement of the process as much as possible. For substances with spontaneous combustion characteristics, measures should be taken to prevent air, water and moisture, or to ventilate, dissipate heat, and cool down. It is strictly forbidden to mix and transport, to prevent the two substances from reacting with each other and causing combustion and explosion. For unstable substances, stabilizers should be added during storage; for flammable and explosive substances with strong diffusivity, alarm devices should be installed.
(2) Fire and explosion prevention measures taken according to the characteristics of the production process

Petrochemical production is mostly carried out in confined equipment. Equipment and pipelines should be inspected frequently to prevent run, run, drip, and leakage. Equipment that is produced under negative pressure should be prevented from inhaling air. In places where explosive gas mixtures are likely to form, ventilation replacement measures can be taken to reduce the concentration of combustibles; inert gas protection measures are used to treat air and shrink during the processing and transportation of flammable solids and the treatment of combustible gas mixtures. Eliminate the flammable concentration and the like formed by combustibles and combustion improvers. In addition, strengthening the control and treatment of inflammable and explosive materials, strict process discipline and operating procedures are also important aspects of preventing fire and explosion accidents.

3. Fireproof and explosion-proof safety device

In order to prevent the occurrence of fire and explosion accidents, prevent them from expanding and reduce damage, many safety devices for fire and explosion prevention and flame and explosion expansion have been developed, and they have been widely used in actual production and have achieved good results. Such as fire-resistant equipment, explosion-proof pressure relief equipment, Mars extinguisher, fire alarms and so on. The specific principles and functions are not introduced here. You can check the relevant information.

4. Preventive measures and emergency measures for fire and explosion accidents

For fire and explosion disasters, the first and foremost policy is prevention, but due to various technical and management reasons and various unforeseen new situations. It is still difficult to completely eliminate fire and explosion accidents in actual production. Moreover, fire and explosion disasters often occur in unexpected moments, and their destructive power and lethality are far greater than other fires. Therefore, from the perspective of safety, there should be corresponding emergency measures, such as emergency cutting of material conveying pipes, venting equipment or Switch to a safe place; temporarily build an overflow-proof embankment, or ditches to direct the liquid flow to a safe zone; eliminate obstacles, leave sufficient safety distance; start fire-fighting equipment; set up temporary disaster prevention organizations, etc., in the event of an accident It can be limited to a certain extent, will not be expanded, and timely take remedial measures to reduce losses.

The above briefly introduces some knowledge about petrochemical fires and prevention. There are still many aspects in this area that cannot be introduced one by one. From the current needs, it is not only the company's own affairs, but also the common responsibility of the whole society to do a good job in fire safety work of petrochemical enterprises, prevent fire and explosion accidents, and protect the safety of the country and people's lives and property.