D类干粉灭火剂的灭火机理研究

Probe into the fire-extinguishing mechanism and efficiency of D powder fire extinguishing media

以灭火机理研究为目的,选取KCl、Na Cl、KBr和Na Br作为基本组分,研究了组分的温升速率、吸热量、初始失重温度及最大失重速率对灭火效能的影响,灭火效能以镁粉燃烧的火焰传播速率和燃烧温度为表征。结果表明:组分的吸热量和初始失重温度越大,灭火效能越好;组分的温升速率和最大失重速率越大,灭火效能越差。温升速率和吸热量与组分的冷却作用有关,良好的冷却效能可以提升金属火灾的灭火效能;初始失重温度和最大失重速率与组分的热稳定性有关,良好的热稳定性可以保证覆盖层窒息燃烧金属,发挥灭火效能。因此,D类干粉灭火剂的灭火机理主要为冷却和窒息。

The given paper takes it as a target to investigate and clarify the mechanism of D powder fire extinguishing media.As a matter of fact,there exists a series of fire extinguishing samples prepared by using the common D powder fire extinguishing media components like KCl,Na Cl,KBr and Na Br.And,in this paper,we would like to trace and determine the fire extinguishing effects and efficiency of such influential factors so as to explore and identify their relation with the extinguishing mechanism.The influential factors of the said D powder fire extinguishing media can be found including the temperature rise rate,the heat absorption rate,the initial weight loss temperature and the maximalized weight loss rate.And,then,the weight loss temperature and the weight loss rate of the samples,say,the DTA( the differential thermal analysis) module can be used to test the heat absorption of the samples.And,for the said purpose,the TGA( the Thermogravimetric Analysis) module has been chosen to measure the thermal related stability.At the same time,the temperature of the samples’ rising rate has also been measured by the author’s own self-designed instrument.And,in terms of testing the fire extinguishing effectiveness,we have also done the magnesium powder fire suppressing experiment via a burning rate tester for dangerous goods.Besides,the flame propagation rate and the flame temperature have also been used as indicators for the fire extinguishing performance.The above mentioned results prove that the different factors may have different effects on the extinguishing efficiency.What is more,the heat absorption and initial weight loss temperature are also positively correlated with the firefighting efficiency and effectiveness,and,so,higher heat absorption and initial weight loss temperature may also contribute to the smaller flame propagation rate and lower combustion temperature,which may also imply better fire extinguishing performance.Hence, the temperature rising rate and the maximum weight losing rate may just go opposite to each other.That is to say,violent temperature rising rate and the maximum weight losing rate can only probably lead to decrease the fire extinguishing efficiency.However,the temperature rising rate and the heat absorption may also be related to the cooling effect of the components and cooling efficiency,which can also promote the firefighting efficiency of the metal fire.Thus,the initial weight loss temperature and the maximum weight loss rate can also be connected with the thermal stability of the components.At this,the fine thermal stability can ensure that the cover layer make stifling effect on the metal fire flame.Therefore,it can be concluded that what the D powder fire extinguishing media can primarily exert is just the fire extinguishing effect through cooling and suffocation.