Common aerosols in nature-clouds, smoke, fog, etc.
The size of particles in aerosol is mostly in the order of 10-5 ~ 10- 1 micron, which has gas fluidity and can spread around obstacles.
The extinguishing agent in the aerosol fire extinguishing device is solid, and the components ejected by the extinguishing agent through oxidation-reduction reaction are aerosols. First generation smoke fire extinguishing
The first generation of aerosol fire extinguishing technology was born in China, also known as smoke fire extinguishing technology, which began in the early 1960s. The smoke automatic fire extinguishing system independently developed by researchers of Tianjin Institute of Public Security and Fire Protection was completed, which was mainly used to extinguish Class A, B and C liquid storage tank fires. This is a brand-new fire extinguishing technology, which is different from the past. There are not only smoke and fog, but also fine solid particles, as well as aerosol substances formed by water vapor and N2 and CO2 fire extinguishing gases.
Second generation k aerosol fire extinguishing
K-type aerosol fire extinguishing technology, also known as potassium salt fire extinguishing technology, is the second stage of aerosol fire extinguishing technology development, which was developed by Beijing Institute of Technology. In this kind of aerosol generator, potassium nitrate is mainly used as the main oxidant, and its spray extinguishing efficiency is high, but because it contains a lot of potassium ions, it is easy to absorb water and form viscous conductive substances. This substance is very harmful to electronic equipment, so the K-type aerosol automatic fire extinguishing device cannot be used in the places of electronic equipment and precision instruments. At present, the usage in the market is rapidly decreasing.
The third generation aerosol fire extinguishing technology
The third generation aerosol (type S) mainly uses strontium salt as oxidant. Unlike the second-generation potassium salt (K-type) aerosol, strontium ions do not absorb moisture, form conductive solutions, and do not damage electrical equipment. This aerosol was independently developed by Shaanxi Jianrui Fire Protection Co., Ltd. (formerly xi Anjianrui Chemical Co., Ltd.) on 1999. 200 1, China mobile communication group company finally chose its strontium salt aerosol (s-type DKL aerosol automatic fire extinguishing device) to protect its communication base station and other places equipped with precision electronic equipment. At present, strontium salt aerosol products have been applied in thousands of engineering projects, so far there has not been an accident of damaging electronic equipment, and the third generation aerosol has been accepted by more and more users. According to the safety industry standard of People's Republic of China (PRC) and People's Republic of China (PRC) "GA499. 1–2004 Aerosol Fire Extinguishing System Part1:Hot Aerosol Fire Extinguishing Device", the main chemical components of aerosol generator filled in the fire extinguishing device can be divided into:
A) S type aerosol fire extinguishing device;
Refers to the fire extinguishing device equipped with aerosol generator containing 35%-50% strontium nitrate and 10%-20% potassium nitrate.
(Model: QRR/SL (floor-mounted), QRR/SG (wall-mounted))
B) type k aerosol fire extinguishing device;
Refers to the fire extinguishing device equipped with aerosol generator containing more than 30% potassium nitrate.
(Model: QRR/KL (floor-mounted), QRR/KG (wall-mounted))
C) Other aerosol fire extinguishing devices. Four elements of combustion: combustible, oxidant, temperature and uncontrolled chain reaction. The extinguishing mechanism of extinguishing gas is to eliminate one or more of the four elements of combustion.
The solid fire extinguishing agent in the S-type aerosol fire extinguishing device is started by electricity, and undergoes redox reaction, forming a large number of agglomerated fire extinguishing aerosols, the main components of which are N2, a small amount of CO2, metal salt solid particles and so on.
The fire extinguishing mechanism of S-type fire extinguishing aerosol is as follows:
First, the mechanism of endothermic cooling fire extinguishing
Metal salt particles absorb a lot of heat at high temperature, and physical endothermic processes such as hot melting and gasification occur, which reduces the flame temperature, and then radiates to the combustion surface of combustible materials to gasify combustible molecules and decompose the gasified combustible molecules into free radicals, thus reducing the combustion reaction speed to a certain extent.
B, chemical suppression fire extinguishing mechanism.
A. Gas-phase chemical inhibition: Under the action of heat, vaporized metal ions or cations that have lost electrons in fire extinguishing aerosol can have affinity reaction with active groups in combustion, repeatedly consuming a large number of active groups and reducing combustion free radicals.
B. Solid-phase chemical inhibition: the particle size of fire extinguishing aerosol is very small (10-9 ~ 10-6m), with large surface area and large surface energy, which can adsorb active groups in combustion, generate chemical reactions, consume a large number of active groups and reduce combustion free radicals.
C, reduce oxygen concentration: N2 and CO2 in fire extinguishing aerosol can reduce the oxygen concentration in combustion, but its speed is slow, and the fire extinguishing effect is far less than endothermic cooling and chemical inhibition. A harmless to human body: the sprayed S-type aerosol fire extinguishing agent is mainly composed of N2, a small amount of CO2, solid particles of metal salts, etc. , are non-toxic.
In actual fire fighting, the spraying process of S-type fire extinguishing aerosol is only about 1 minute, and the fire fighting time is only 2-3 minutes, which is harmless to human body.
B. High fire extinguishing efficiency, no secondary damage to electrical appliances: The fire extinguishing mechanism of S-type fire extinguishing aerosol is mainly endothermic cooling and chemical suppression, so its fire extinguishing efficiency is high.
S-type aerosol is strontium (Sr) salt aerosol, and the decomposition products of its main oxidant strontium nitrate are SrO, Sr(OH)2 and SrCO3. These three substances will not absorb the moisture in the air, so they will not form a conductive and corrosive electrolyte film, thus avoiding the damage to the equipment.
The surface resistance of K-type and S-type fire extinguishing agent accessories should be no less than1mΩ and 20mΩ respectively (above1mΩ is an insulator).
C Less fire extinguishers: the general dosage of aerosol fire extinguishing agent is about 130g/m3, and that of other gas fire extinguishing agents is 300- 1000g/m3.
For example, HFC-227ea is 530g/m3.
D. Save weight and space: Because it is stored at normal pressure, the volume and weight of aerosol fire extinguishing system are greatly reduced. Its weight is only 1/40 of that of inert gas, and its space is only115.
E. Environmental protection: Aerosol fire extinguishing agent does not contain substances that damage the atmospheric ozone layer, and its ODP and GWP values are zero, so it is an ideal halon substitute at present.
F. Simple installation and extremely low maintenance cost: Compared with other gas devices, the aerosol fire extinguishing system only needs some wires to connect, so the installation is extremely convenient and simple, saving man-hours 1/3 or more. Because there are no high-pressure vessels, valves, nozzles, etc. The maintenance cost is extremely low.
G. Cost saving: Aerosol fire extinguishing system has the lowest cost among gas fire extinguishing products because of its light weight, small occupied space, simple installation, atmospheric storage and negligible maintenance cost.