Abstract : Some brief introductions about the fire characteristics of triethylaluminum and the extinguishing mechanism of dry powder fire extinguishing agent against triethylaluminum are given.
Keywords: triethylaluminum; dry powder fire extinguishing agent; ultra-fine powder; automatic fire extinguishing device
I. Overview
Triethylaluminium is chemically active, flammable and explosive. This kind of dangerous goods storage equipment, warehouse fire extinguishing work. It has always been a problem for domestic and foreign firefighters. Due to the special properties of the objects to be protected, the fire extinguishing agents used for such first class spontaneous combustion items are very limited. Traditionally, they can only be covered with non-combustible materials such as dry sand or vermiculite. Or absorption, slow fire extinguishing, low efficiency; due to the high risk of fire, people are not accessible, people often face such fires and helpless. In recent years, the fire protection industry began to use dry powders to extinguish fire protection. This kind of chemical fire prevention and fire extinguishing technology has made certain progress. The nature of the protected object that is burning in air or exploding when it encounters water has virtually formed the extinguishing agent. Special requirements, fire extinguishing agents for such fires are currently limited to dry powder fire extinguishing agents, and most of the fire extinguishing capabilities are flawed.
At present, some domestic chemical companies in the production and storage of petrochemical products, fire safety has always been an important concern of long-term attention, every year has invested a lot of manpower and material resources to ensure the safety of oil and chemical raw materials reserves; foreign triethyl aluminum The study of chemical fires was relatively early. Some countries such as the United States, Germany, and Israel had special dry powders to extinguish such fires. The high price of fire extinguishing agents, coupled with the high cost of equipment and engineering design, made most companies discouraged. Wuhan Green Fire Equipment Co., Ltd. has developed a brand new ultra-fine dry powder fire extinguishing agent. According to the experts of the national authoritative testing organization, it has unique advantages and characteristics in preventing and extinguishing triethylaluminum chemical fires. Here, the author He gave his personal insights on the prevention and suppression of triethylaluminum fires.
Second, the characteristics of triethyl aluminum
Triethyl aluminum (English name: Aluminum Triethyl) colorless transparent liquid, melting point: -52.5 °C, boiling point: 186 °C/101.3Kpa, flash point: <-52 °C, ignition temperature <-52 °C, stability: in Nitrogen is stable and safe at temperatures below 120°C and is soluble in paraffinic hydrocarbons. It has no pyrophoricity when the concentration of triethylaluminum is below 15% (m/m); incompatible materials: air, water, active hydrogen Compounds, halogens or halogen compounds, carbon dioxide, etc. Conditions for avoiding contact: High temperatures above 120°C, air. It is chemically active, reacts violently with oxygen, spontaneously ignites in air, decomposes into aluminum hydroxide and ethane when exposed to water, and reacts violently with acids, halogens, alcohols, and amines. It has a burning effect on the human body and is thermally stable. Poor performance, mainly used for organic synthesis, also used as rocket fuel. The first-grade spontaneous combustion product emits smoke in the air and can spontaneously ignite. It is sensitive to moisture and trace oxygen and can easily cause explosions. It has strong stimulation and corrosion effects on the human body. Damage to the respiratory tract and conjunctiva, high concentrations of inhalation can cause pulmonary edema. Inhalation of smoke can cause fumes. Skin contact can cause burns, congestion, edema, and blistering pain.
Application of triethyl aluminum
a) for military use
Weapons: Before the 1970s, the U.S. was equipped with a liquid column firearm. After 1969, the United States has adopted rocket combustion as an alternative to the traditional liquid column firefighting method. In the early 1970s, the United States began to transform the XM191 multi-portable flame throwers into flame weapons. The weapon was used in design drawings, field experiments, small-batch production, and battlefield evaluation. It took a total of less than three years. In the mid-1970s, the weapon was designated as M202 flame weapon and began to be used by the US Army and Marine Corps. What is equipped now is a slightly improved M202A2 type. The M202-combustion rocket launcher consists of a rocket launch tube and a rocket-elastic clip. It uses a self-igniting combustion agent, triethylaluminum, and is powered by the M54 rocket engine.
Ammunition: Combustion rockets are 535mm long. The warhead contains 600g of thickened triethylaluminum combustible. It is equipped with a mechanical trigger fuze and uses the M54 rocket engine to propel projectiles. With this kind of combustion agent, it will explode when water is ignited. This will not only save the ignition system, but also increase the difficulty of extinguishing the fire. Even if it is temporarily covered with sand, it will still burn when it encounters air. It also has a certain degree of adhesion, is not easy to remove, and adapts to battle requirements.
Flaming Bombs: Aviation bombs, artillery shells, rockets, rifle grenades, and grenades containing a burning agent. Also known as arson bombs. It is mainly used for burns and has the power to burn down flammable military technology equipment and equipment. It is usually composed of an elastomer, a burning agent, an explosive or a projectile, a fire tube, a fuse, and the like. The combustion agent is mostly made of aluminum heat agent, yellow phosphorus, naphtha, thickened triethyl aluminum and thickened gasoline. It is used to generate high-temperature flames and damage the targets. The projectile or explosives are used to bomb the projectiles and the combustion agent is used. Ignited and scattered to the target. The most commonly used in modern battlefields is the burning of aviation bombs. Commonly used are mixed-burning aviation bombs and napalm aerial bombs. The former is packed with thickened triethylaluminum, which has a smaller body and a shell weight of about 10 to 50 kg. The latter is equipped with napalm and yellow phosphorus, and has a weight of up to 500 kg. The number of types of modern incendiary bombs is increasing day by day. The heat generated by the combustion agent and the burning time are constantly improving. The thickened triethylaluminum is one of the main raw materials.
b) for chemical production
At present, triethylaluminum is widely used in the organic synthesis of the chemical industry, such as activators of polypropylene plastics and other products, because of different purposes, the purity is not the same, the domestic large-scale chemical companies are using triethyl aluminum With triethylaluminum storage tanks and devices, triethylaluminum is usually stored at no pressure. Nitrogen is used for pressure-feeding to process equipment during production and use. Its pressure is generally not more than 0.2Mpa, and it is restored to zero at the time of production shutdown. Pressure state requires good sealing of tanks and pipelines. Once a leak occurs, a fire will occur. Traditional type fire extinguishing equipment has been unable to cope with the fire of such special products. Previously, chemical companies have been troubled by this type of fire. Fire safety and security work for a self-ignited item fire.
Four, triethyl aluminum fire prevention
The characteristics of triethylaluminum do make people feel a little scary, and it brings safety and security to the operators, and it brings difficulties to the safety management of the company. However, as long as we understand the basic characteristics of triethylaluminum, then we should fire it. Protection is not difficult, first of all, in terms of training the basic knowledge of the operators, let the operators know how to handle accidents accidentally, familiarize themselves with the process of the equipment, and be unrestrained in the event of an accident. The second is to establish a sound security system. Non-operators are prohibited from accessing triethylaluminum equipment. They are required to be transferred on duty strictly to prevent a vacuum in safety. Third, equipment dry powder type automatic fire extinguishing device, to prevent accidents, through modern electronic monitoring technology, the three-aluminum storage tanks and equipment for all-weather monitoring, a fire that is an alarm and can automatically control the fire.
V. Formation of triethylaluminum fire and its fire extinguishing mechanism
The triethylaluminum fire is mainly caused by the leakage of equipment or pipelines. During the production process, the pressure in the triethylaluminum storage tank and the pipeline is 0.2 Mpa. Once the seal is not tight, leakage will occur. Ethyl aluminum will burn in contact with air. If it is not extinguished in time, it will result in a large fire. Therefore, to reduce the fire damage, it must be required that the fire extinguishing agent and the fire extinguishing device can quickly suppress, early discover, and effectively extinguish the fire.
Dry powder (especially superfine dry powder with high fire extinguishing efficiency) is effective for triethylaluminum fire. Its fire extinguishing mechanism is mainly based on chemical fire extinguishing. It can extinguish flames through chemical and physical dual fire extinguishing functions in triethyl aluminum storage tanks or When a fire occurs in the pipeline, the cloud-shaped ultra-fine dry powder extinguishing agent powder released by the automatic fire extinguishing device comes into contact with the combustion flame to generate a chemical reaction to capture free radicals and heat, thereby cutting off the combustion chain and extinguishing the flame. A large amount of glassy substances generated by the reaction between the agent and the flame adsorbs on the surface of triethylaluminum to form a separating layer, thereby physically isolating the protected object from the air and blocking the oxygen required for reburning. In order to prevent re-ignition; when the fire extinguishing agent is injected into the fire field to extinguish the fire, the nitrogen pressure in the triethylaluminum storage tank should be quickly cut off, so that the triethylaluminum storage tank can be in a non-pressure state to prevent the dry powder coating from being The gas pressure broke and renewed.
Sixth, the application of triethyl aluminum fire extinguishing agent and automatic fire extinguishing device
1) Fire extinguishing agent
Extinguishing agents that can extinguish triethylaluminum fire are mainly dry powder fire extinguishing. The dry powders currently used in the market are generally divided into: ABC ordinary dry powder, BC ordinary dry powder, D dry powder (special dry powder), ultrafine dry powder and so on.
1ABC and BC dry powder common dry powder flow performance, poor water repellent performance, fire extinguishing efficiency is also low, easy to absorb moisture and agglomeration, BC dry powder can only be used for oil and gas fires, and ABC dry powder is ammonium phosphate as the main ingredient, Residual acidic covering during fire extinguishing has corrosive effect on metal. Its particle size is in the range of 60-70μm. The effect of full flooding is poor. It can only be used for portable, cart-type and other mobile fire extinguishers, so it is for triethyl aluminum. For fire protection, ammonium phosphate dry powder extinguishing agents are basically no longer used.
2D dry powder is a dry powder fire extinguishing agent for fighting metal fires. Its main components are borax, sodium chloride, potassium chloride, barium chloride, sodium carbonate, and graphite. Due to the low melting point of sodium carbonate, a thin film can be formed on the surface of the burning metal, so that the burning metal is isolated from the surrounding air and the fire is extinguished. At present, there are few domestic production, and the imported dry powder D mainly comes from the United States, Germany, Israel and other countries. In fact, the requirements for extinguishing triethylaluminum fire are the fire-extinguishing efficiency and the extinguishing speed, because triethylaluminum needs to react with oxygen to generate combustion. In other metal fire burning methods, D dry powder (so-called special dry powder) is not as effective as ordinary ABC dry powder, but the price is nearly 200 times that of normal dry powder. In terms of cost performance, there is no such need, and Many domestic enterprises have been difficult to accept. According to relevant sources, some domestic design and construction companies are keen on imported products, and the owners are unacceptable in terms of price, often resulting in a situation where only design is not installed. Some people even suspect that imports are used. The incommensurability of the price of the product gives some unscrupulous elements the opportunity to benefit from the medium and large fishing.
3Ultrafine dry powder fire extinguishing agent is a new type of high-efficiency fire extinguishing agent completely different from ordinary dry powder. It is non-toxic and harmless. It is non-irritant to human skin and has no corrosion to protective objects. It does not decompose or absorb moisture under normal conditions. , No caking, a new fire extinguishing agent with good fluidity, dispersibility and electrical insulation, especially the ultra-fine dry powder fire extinguishing agent developed by Wuhan Green Fire Equipment Co., Ltd., with an average particle size of less than 5μm, the fire-extinguishing efficiency is 6-10 times that of ordinary dry powder; it differs from ordinary ABC dry powder fire extinguishing agent in that it can be naturally damp-proof and does not need to be wrapped with silicone oil. The particle size can be processed to 5μm or less, and the full-submerged fire extinguishing performance is very good. It has high fire-extinguishing efficiency and fast fire extinguishing speed. , low fire extinguishing concentration and other characteristics, the dry powder fire extinguishing extended to the field of automatic fire extinguishing; According to information from the Tianjin Fire Research Institute, the current domestic Wuhan Green Fire Equipment Co., Ltd. ultra-fine dry powder fire extinguishing agent according to the Ministry of GA761-2005 new standards It can completely extinguish the triethyl aluminum fire.
2) Fire extinguishing device
There are many kinds of dry powder automatic fire extinguishing devices, and more dry powder automatic fire extinguishing devices are used. There are ultra-fine dry powder and no pipe network fire extinguishing series (including suspended, wall-mounted, cabinet type) and ultra-fine dry powder pipe network series.
1Using gas-fired ultra-fine dry powder automatic fire extinguishing device (also called pulse start or supersonic start, filled with dry powder of ammonium phosphate salt): The main feature of this kind of automatic fire extinguishing device is to drive by gas, when the protection zone occurs In the event of a fire, the fire ignites the fuse (or heat-sensitive cable), and the explosive powder in the device explodes instantaneously, generating a large amount of gas to push out the dry powder fire extinguishing agent; its application more successfully solves the problem of agglomeration of ammonium phosphate dry powder. And can achieve the purpose of rapid fire extinguishing. However, there are still obvious defects: First, there is no fundamental solution to the inherent defects of the ammonium phosphate dry powder on the protection of the protective material, such as corrosion, difficult to remove, and poor overall inundation; second, the huge explosion sound and shock wave generated by the gunpowder Injury of objects, some places need multiple linkages, and huge shock waves and flares are very likely to cause secondary disasters, especially explosion-proof places of chemical companies, and are therefore banned in explosion-proof places.
2 nitrogen-driven ultra-fine dry powder automatic fire extinguishing device: This type of fire extinguishing device is powered by nitrogen, which drives the superfine dry powder fire extinguishing agent in the fire extinguishing device to spray; it is a silent start, similar to gas extinguishing, nitrogen pressure is 1.2MPA, Safe and reliable, without any damage to the protection, in addition to the green characteristics of fire extinguishing agents, its high fire extinguishing efficiency, fast fire extinguishing, low fire extinguishing concentrations fully meet the requirements of today's fire safety, and nitrogen is just right for triethyl aluminum Safe; The important thing is that this fire extinguishing device has a high technological content. Suspension type, cabinet type, wall type, pipe network type can all interface with the fire alarm system to form an automatic fire extinguishing system; its pipeless network fire extinguishing system (suspended, Cabinet-type, wall-mounted) Easy installation and low cost; both pipe network and non-pipe network can extinguish fires in large spaces, flexible application of full-submerge fire extinguishing or partial protection fire-fighting; there are multiple startup methods: electronically controlled startup , constant temperature start. It can be flexibly used according to the site environment and has a wide range of applications; the activator workshop of Sinopec Wuhan Branch all the triethylaluminum storage tanks were all installed in March 2005 by Wuhan Green Fire Equipment Co., Ltd. Suspension type pipeless automatic The fire extinguishing system, according to the introduction of the company's safety department, installs Wuxi Green Fire Company's automatic fire extinguishing system without pipes, which is nearly 70% cheaper than the original installation of imported equipment. The operation of the alarm and fire extinguishing equipment is normal for nearly one year. The safety of daily production is carried out.
Seventh, conclusion
Superfine dry powder fire extinguishing agent after a large number of tests can extinguish the need for oxygen to help the metal fire, triethyl aluminum fire is not terrible, the domestic fire fighting companies are fully capable of dealing with such fires, such as Wuhan Green Fire Company's ultra-fine The dry powder fire extinguishing agent has more advantages in its technology. It represents the current high level and the development direction of the dry powder fire extinguishing in the dry powder fire extinguishing. The ultrafine dry powder fire extinguishing agent and the automatic fire extinguishing device are the current extinction of triethyl aluminum fire in China. The best plan.