Study On Fire Extinguishing Effectiveness Of Sodium Bicarbonate And Ammonium Phosphate Powder Based Fire Extinguishing Media

Today,with the rapid development of science and technology and economy,the number of high-rise buildings,large libraries and electronic equipment is also increasing,the types and styles of buildings are becoming more diversified,and the materials used are more complex.Correspondingly,the fire environment is more complex and changeable,which has to attract people’s attention.Under the background that Halon has been eliminated,it is urgent to develop a new type of fire extinguishing agent which can replace Halon fire extinguishing agent,and make an in-depth study on its fire extinguishing effect and fire extinguishing mechanism,in order to deal with the increasingly complex fire environment,so as to protect the safety of buildings and people’s lives and property.Compared with other fire extinguishing agents,dry powder fire extinguishing agent has become an excellent substitute for Halon fire extinguishing agent because of its low cost,high fire extinguishing efficiency,environment-friendly and easy to use.In order to further improve the fire extinguishing efficiency of dry powder fire extinguishing agent,sodium bicarbonate and ammonium phosphate were selected as the research objects.Exploratory experiments were carried out to improve the fire extinguishing performance of powder by reducing the particle size of powder,preparing new composite powder and gas-solid coordination.Through the powder fire extinguishing experimental platform,the critical fire extinguishing concentration of typical sodium salt and ammonium phosphate to inhibit methane fire was measured,the flame change was observed,and its physical and chemical fire extinguishing mechanism was analyzed.Under the action of carbon dioxide,nitrogen,helium and argon four inert gases,synergistic fire extinguishing experiments were carried out with ultra-fine sodium bicarbonate powder and ultra-fine ABC dry powder respectively,and their synergistic fire extinguishing effect was studied.The specific conclusions are as follows:(1)the critical fire extinguishing concentration of typical sodium salts is in the following order:sodium carbonate<sodium chloride<4μm sodium bicarbonate<10μm sodium bicarbonate<48μm sodium bicarbonate(unextinguished),with the decrease of the particle size of sodium bicarbonate,the critical fire extinguishing concentration gradually decreases and the fire extinguishing efficiency increases;after refinement and modification,the inhibitory effect of sodium carbonate and sodium chloride on methane fire is better than that of 4μm sodium bicarbonate.The critical fire extinguishing concentration of typical ammonium phosphate is in the following order:diammonium hydrogen phosphate<triammonium phosphate<ultrafine ABC dry powder<ammonium dihydrogen phosphate<ammonium polyphosphate.(2)When the concentration of magnesium hydroxide powder alone reaches149.4g/m~3,the methane flame cannot be completely extinguished.When the ratio of sodium bicarbonate to magnesium hydroxide reaches 1:0.15,the critical fire extinguishing concentration of the composite powder reaches the minimum of28.2g/m~3,but on the whole,the addition of magnesium hydroxide can’t increase 4μm the extinguishing efficiency of sodium bicarbonate;(3)When the volume fraction of carbon dioxide,nitrogen,helium and argon are5.4%,8.8%,5.5%and 14.6%respectively,the synergistic effect of ultrafine ABC dry powder and inert gas is the best;When the volume fraction is 7.1%,6.4%,8.5%and 10.1%respectively,sodium bicarbonate and inert gas have the best synergistic effect.Under the best synergistic effect with carbon dioxide,the consumption of fire extinguishing agent can be reduced by 80%compared with sodium bicarbonate and ultra-fine ABC dry powder alone;(4)When the volume fraction of carbon dioxide,nitrogen,helium and argon are5.4%,8.8%,5.5%and 14.6%respectively,the synergistic effect of ammonium dihydrogen phosphate with four inert gases is poor compared with ultrafine ABC dry powder,while ammonium sulfate can not extinguish the flame,which indicates that there are other effective components in ultrafine ABC dry powder which can have synergistic effect with inert gases.