Halocarbon (halon) fire extinguishing agent, a non-cyclic saturated hydrocarbon compound containing chlorine, bromine and other halogens. Halon 104 (carbon tetrachloride) was first used as an extinguishing agent to fight flammable liquid fires, and then halon 1001, 1011 and 2402 were developed to protect military installations. These early halon extinguishing agents produced toxic gases when extinguishing fires, causing injury and death, and the search for safer and more reliable halogenated extinguishing agents began. Halon 1301 (trifluoromethane) and 1211 (difluorochloromethane) solved the safety problem. These two extinguishing agents were highly effective, non-toxic, non-conductive, fast evaporating, residue-free, clean and safe, and began to be widely used in fire fighting.
The chlorine and bromine atoms generated by the decomposition of halon fire extinguishing agents will catalyse the conversion of the more active ozone molecules into stable oxygen molecules, and the chlorine and bromine will continue to deplete the ozone on the one hand and regenerate it on the other, destroying the ozone layer.
In order to protect the ozone layer, most countries in the world have signed the Vienna Convention for the Protection of the Ozone Layer, the Montreal Protocol on Substances that Deplete the Ozone Layer and other international conventions such as the London and Copenhagen amendments. After several amendments, it is clearly stipulated that the phase-out of halon fire extinguishing agent in developed countries will be on January 1, 2000 and in developing countries on January 1, 2010. China has joined the ranks of the Parties to the Montreal Protocol (Amendment) in June 1991. According to the National Programme for the Phase-out of Ozone Depleting Substances in China, China will stop producing Halon 1211 fire extinguishing agent in 2005 and Halon 1301 in 2010. With the implementation of the “China Fire Protection Industry Halon Phase-out Plan”, the production and consumption of halon has been drastically reduced, and it is particularly urgent to develop clean and efficient environmentally friendly alternatives to halon fire extinguishing agents.
At present, at home and abroad have been used and being developed to replace the halon gas fire extinguishing system (agent) are: high and low pressure carbon dioxide fire extinguishing system, heptafluoropropane (FM200) fire extinguishing system, SDE solid into gas type gas fire extinguishing system, smoke and ashes (Inergen) fire extinguishing system, aerosol EBM fire extinguishing system (device), etc., is being developed to develop the halogen 13001 trifluoroiodomethane (CF3I) fire extinguishing system, trifluoromethane fire extinguishing system, (ultra) fine water mist fire extinguishing system, etc..
Halothane 13001 trifluoroiodomethane (CF3I) is a new type of gas fire extinguishing agent to replace halon. CF3I is mainly used for chemical fire extinguishing, mainly through the thermal decomposition of the iodine group generated to participate in and destroy the chain reaction of combustion, so as to achieve fire extinguishing effect.
Reaction formula: CF3I → CF3+I-
RH+I-→ HI+R-
OH-+HI → H2O+I-
CF3I can also play a certain role in the fire extinguishing process of physical extinguishing. In general, the larger the molecular weight of the extinguishing agent, the greater the heat of evaporation. CF3I is stored in a high pressure liquid form (molecular weight: 195.91, boiling point:-22.5°C), and when the extinguishing agent is released, it transforms from a liquid to a gaseous state and needs to absorb a large amount of heat, which has a significant effect on the cooling of the fire.
CF3I is the least toxic of all halogenated alkanes and has the lowest fire extinguishing concentration (3.2%), and can be decomposed in the atmosphere in just one day, making it an environmentally friendly alternative.
The efficiency of CF3I is one of the highest among all extinguishing agents. According to the method of determining the fire extinguishing design concentration of Halon 1301: on the basis of the minimum fire extinguishing concentration and then increasing the insurance amount of CF3I by 70%, it can be concluded that the fire extinguishing design concentration of CF3I is 5%, which is lower than the fire extinguishing design concentration of Halon 1301 (5%-7%). In addition, due to the higher boiling point of HFCI, it is present in the gas pipeline in a liquid form for a longer period of time than Halon 1301 and therefore requires less resistance to flow, allowing the gas to reach the fire extinguishing position in a shorter period of time, thus implementing fire extinguishing at a faster rate. CF3I is a clean fire extinguishing agent. CF3I has low toxicity. CF3I has a good volatility, it has the characteristic of disappearing easily after vaporization. The strongest absorption peak of the carbon iodine bond in the chemical structure of CF3I is near 260nm, which is much larger than that of the carbon-bromine and carbon-chlorine bonds, and the carbon-iodine bond also has some absorption in the near-UV region, so its photolytic It is also measured that the carbon-iodine bond does not stay in the atmosphere for more than one day and has no chance of causing a “greenhouse effect”, with an ozone depletion potential of GWP <5.
CF3I fire suppression systems are more expensive. Due to the high viscosity coefficient of trifluoroiodomethane, the transport distance is limited and it can only be used as a stand-alone system and without a pipeline network, so its comprehensive cost is much greater than 1301, FM200, SDE, aerosols, etc. At the same time, when spraying and releasing, like FM200, it forms a “white mist”, which affects the evacuation of people to a certain extent.
Fluoromethane gas is currently one of the better clean extinguishing agents used to replace halon. The following are the characteristics of the gas fire extinguishing system. It is a good insulating substance as it is non-conductive. It is extremely beneficial for extinguishing electrical fires and fires in places with live working equipment. For example, generator rooms, substations, oil-immersed transformer rooms, computer rooms, communication hubs, telephone switchboard rooms, etc. Trifluoromethane is non-corrosive, non-polluting and non-damaging to the material it protects after extinguishing a fire. Especially for tobacco store, tobacco production workshop, food store, data room, archive room, book store, finance room, vault, printing workshop, paper store, cotton textile and fur store, etc., there is no pollution to the protected items after fire extinguishing and they can still be used. Trifluoromethane is stable, does not deteriorate in long-term storage, is harmless to people and can be used in places where people work. It is fast and effective in extinguishing fires. It can be used as permanent fire extinguishing equipment in flammable production workshops. For example, in hydraulic equipment, drying equipment, paint spraying lines, electrical ageing rooms, coal dust silos in power and cement plants, underground parking garages, boiler rooms and ships’ cabins and cargo bins, etc., the use of Methane-trifluoride gas fire extinguishing systems has a very good effect on fires. The temperature range is -20~+50℃, and the designed extinguishing concentration is 13.6%-50%. The minimum amount of extinguishing agent required per unit volume of protected area is 550 grams, which is 13% lower than the standard amount of 634 grams of Heptafluoropropane, and the price of extinguishing agent is much lower than that of Heptafluoropropane.
