粉尘爆炸特征和预防措施探讨

随着现代工业的发展,粉末技术得到了广泛应用,使得粉末产物日益增多.许多粉体加工企业对粉体的相关危害知识没有深刻的认识,这些物质在安全生产、储存、运输和应用过程中,安全管理比较混乱,没有做到很好的防护,缺乏必要的防火防爆设施,再加上操作人员思想上的麻痹大意.粉尘爆炸的危险性大大增加,粉尘爆炸的事故也频繁发生.粉尘爆炸具有很强的破坏力,往往造成重大人员伤亡和严重损失,已经越发成为工业安全不可忽视的重要问题.本文从粉尘爆炸的基本特征出发,论述了粉尘爆炸的机理、条件、特点.根据粉尘爆炸需要的条件,从可燃物、助燃物和点火源三个方面,提出了在实际生产中,预防粉尘爆炸的一些具体措施,以期指导安全生产.     

超细冷气溶胶抑制油气预混爆炸实验研究

大型油罐区火灾事故往往伴随着油气爆炸,对应急救援消防官兵生命安全带来威胁.具有可压缩性、流动性和弥散性特征的超细干粉冷气溶胶对泄漏可燃油气爆燃爆轰有抑制作用.采用三路进气20L球试验装置模拟油气-空气与超细干粉冷气溶胶预混点火燃爆过程,实验结果表明:超细干粉冷气溶胶具有物理和化学双重抑爆作用,随着抑爆剂用量的增大其最大爆炸压力和最大爆炸压力上升速率呈下降趋势,且爆炸感应期明显被滞后;抑爆过程油气爆炸指数快速下降后趋于稳定,抑爆效果与超细粉体本身特性、抑爆剂用量及油气点火时刻有关.该研究有助于优化油气环境的最佳抑爆条件,对大型储油罐区油气防火防爆防护和抑爆技术的应用具有积极意义.     

Efficiency characterization of fire extinguishing compound superfine powder containing Mg(OH)2

To improve the fire extinguishing efficiency of existing dry powders, a new type of superfine dry powder was prepared using magnesium hydroxide as an additive. In our study, a thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to analyze the thermal decomposition of the synthesized powders. The temperature of thermal decomposition, weight loss, and other thermodynamic parameters of the fire extinguishing powders were analyzed to explain the performance advantages of the compound superfine powder. Through a small-scale fire experiment, the physical parameters of the extinguishing process—such as extinguish time, powder dosage, smoke concentration, and minimum extinguishing concentration—were quantified for the suppression of a diesel fire using the different powders; these parameters were used to evaluate the fire extinguishing capacity and toxic gas suppression ability of the powders. TGA demonstrated that the compound superfine powder decomposed more quickly and its thermal decomposition process was much shorter than those of the other powders. The DSC data indicated that the compound superfine powder could decrease the characteristic temperature at each stage and thus the powder absorbed the flame's heat more quickly and suppressed flame propagation. The fire extinguishing test demonstrated that the consumption of the three types of fire extinguishing powder decreased with an increase in the driving pressure, and the order of powder dosage was as follows: commercial dry powder > superfine powder > compound superfine powder. Similarly, the order of minimum extinguishing concentration was as follows: commercial dry powder > superfine powder > compound superfine powder. Furthermore, the compound superfine powder exhibited a greater capacity for controlling toxic and harmful gas emissions.     

N2和CO2抑制煤燃烧火焰特性对比试验研究

为了研究N_2和CO_2气体灭火剂在抑制煤明火燃烧特性方面的不同,通过搭建受限空间煤明火燃烧试验,分别开展了11.97%、16.81%、20.76%的N_2和10.79%、14.89%、20.32%的CO_2作用下煤明火燃烧抑制试验。鉴于火焰表面积变化与热释放速率变化呈正相关,基于火焰图像分析法开展试验研究。试验过程中,首先,通过数码摄像仪记录不同体积分数惰性气体作用下煤燃烧火焰面积的变化,然后利用Matlab软件进行火焰图像特征提取和"对比度增强"预处理,消除图像记录过程中存在的噪声,以便于有效进行火焰目标识别;其次,基于"阈值法"原理,利用Image-Pro Plus软件对预处理过的火焰目标进行识别和计算,进而实时获得试验过程中火焰表面积;最后,使用小波变换理论对火焰表面积变化曲线进行消噪处理,以获得火焰表面积变化趋势及主要波动信息。结果表明,CO_2比N_2具有更好的熄灭煤明火燃烧的能力,CO_2作用下煤火火焰表面积呈现指数下降,而N_2作用下呈现直线下降,且CO_2的灭火时间比N_2缩短了25%以上。该试验结果明确了N_2和CO_2在熄灭煤明火特性上的不同,弥补了CO_2仅比N_2具有更好的抑爆特性的认识。     

干水在热环境中的持续作用效果研究*

为研究干水对建筑火灾中高聚物燃烧产生的热危害和烟气危害的影响,采用火焰传播量热仪（FPA）模拟建筑火灾扑灭后的持续热环境,对灭火过程中过量施加的干水对可燃高聚物的持续作用效果进行研究。结果表明:干水能够明显提升可燃物的抗复燃性能以及削弱燃烧过程中的热危害和烟气危害;相比于纯燃料,干水作用下可燃物的点燃时间出现明显的延迟,并且热释放速率和一氧化碳生成速率明显降低,尤其在可燃物燃烧初期,干水还具有显著的抑制烟气生成速率的效果。研究结果可为灾后消防人员的搜救和被困人员的逃生提供一种新的技术方案。     

涡喷消防车在化学事故中的抢险救援功能

我国化学工业中的有毒气体的泄漏 ,化学品爆炸、失火等特种灾害的发生频度随化学工业的发展速度而同步增长。涡喷消防车是一种特大功率的气体、洗消剂、灭火剂的喷射平台 ,在化学事故的抢险救援中 ,对吹散、稀释、洗消事故现场的有毒气体 ,强制通风、驱散有毒烟雾和火场降温有独特功能 ,有利于赢得抢险救援的宝贵时间。在防毒抢险和消防救援中 ,在保护人民生命安全和消除毒害及爆炸事故方面有其重要作用。     

提高水基热气溶胶灭火剂燃速途径的研究

水基热气溶胶灭火剂是以替代哈龙为目的而研制的新一代气溶胶灭火剂；因为其燃烧速度对灭火效率有重大影响，故本文在理论分析的基础上，采用加入金属粉提高导热系数，增加反应放热量；加入正催化剂降低反应活化能；在反应器中采用导流管除去燃烧表面的液态产物，加强燃烧反应的热反馈等方式提高灭火剂燃速。     

阻化注浆在硫化矿床自然发火治理中的应用

为治理大厂铜坑矿细脉带硫化矿石自燃火灾,提出喷洒添加NCZ-1型防火阻燃剂的阻化泥浆灭火方法;依据该矿具体条件设计了喷洒工艺流程,测定单位体积阻燃剂用量及各指标气体浓度等参数,研究注浆法在自燃火灾治理中的应用问题。结果表明:该防火阻燃剂在金属矿山火灾治理中效果较好;喷洒阻化泥浆后,环境质量明显改善,主要有害气体SO2浓度减少47.16%;CO2浓度减少了58.49%;阻化期可达14～20天。该试验成果及使用方法对非煤类含硫矿床自燃治理研究有一定借鉴意义。     

超细微粒灭火剂抑制单室火灾的试验研究

通过试验测量燃烧区温度的变化过程,研究了超细微粒灭火剂在单室火灾模型下与4种不同类型火焰的相互作用、灭火时间和效果。结果表明,超细微粒灭火剂具有较好的全淹没灭火能力。当1 000g超细微粒灭火剂施放后,位于微粒灭火剂流动路径上的无遮挡火焰(中央火和角落火)能够被迅速扑灭,灭火时间分别为3.9 s和7.2 s;对于火源功率较小的顶棚火,由于火羽流及热泳力的作用,微粒灭火剂能迅速扩散到顶棚,从而能在短时间内将其扑灭,灭火时间约6.3 s;对于遮挡火,其灭火时间较长,约14.3 s。微粒灭火剂浓度对灭火时间有较大影响。当微粒灭火剂的喷射质量为500 g时,虽然中央火、角落火和遮挡火均能被扑灭,但灭火时间都较喷射1 000 g灭火剂时有较长的延长,灭火时间分别为8.1 s,13.9 s和22.2 s。对于需要灭火剂微粒扩散较远距离后灭火的顶棚火,虽然灭火剂在热羽流和热泳力作用下能扩散到顶棚,但因浓度太低,同时由于其他3处火焰熄灭后,灭火室内的氧气消耗速率降低,从而使顶棚火得到足够的氧气,燃烧反应进一步加强,温度反而逐渐升高,不足以将其熄灭。     

气体、粉尘爆炸灾害及其安全技术

对可燃性气体、蒸汽、粉尘的爆炸特性及其抑爆、隔爆安全技术进行了系统的研究 ,并对常见的可燃性气体、蒸汽和粉尘的各种爆炸特性参数和气体抑爆安全技术参数进行了实验测定。根据实验测定结果得到的结论对这种可燃性物质的安全应用具有重要的参考价值     

Law of variation for low density polyethylene dust explosion with different inert gases

To reveal the effects of different inert gases on explosion characteristics during low density polyethylene (LDPE) dust explosion and optimize the explosion-proof process, eight N₂ (CO₂)/air mixed inerting conditions were experimentally studied. Typical inerting conditions with 12 L cylindrical explosive tank were used to study the characteristics on the flame propagation. The thermogravimetric analysis with related theories were used to further explain the mechanism and quantities in low density polyethylene (LDPE) dust explosion with different inert gases. The results showed that the reduction of O₂ concentration could effectively delay the progress of flame growth process and weaken the effect of dust combustion reaction. The flame growth process of condition (N₂/air (18% O₂)) was 2.05 times slower than that of the non-inert condition. The explosion strength was obviously reduced, and the characteristic parameters such as explosion pressure and flame propagation speed were also affected by the decrease of O₂ concentration. For LDPE powder, the smaller the median diameter, the greater the explosion intensity and the lower the limiting oxygen content (LOC). The LOC with CO₂ was usually higher than that with N₂ and the effect of CO₂ was significantly better than N₂ in inerting.     

A study of the probability distribution of pool fire extinguishing times using water mist

Water mist, a replacement for Halon gaseous agents in fire fighting, has been studied for decades. However, the fire-extinguishing reliability of water mist is debated. For example, there are significant differences in extinguishing times between tests conducted under the same conditions, and water mists have difficulty extinguishing small fires. To date, no study of the probability distribution of extinguishing times has been reported. In this study a statistical analysis of the extinguishing time distribution of pool fires extinguished using water mist is presented. The fire sources were circular/square stainless steel pans with gasoline, diesel, ethanol or daqing RP-3 as fuel. Two types of extinguishing scenarios were observed. In one situation, the fire was extinguished via a blow off process, when the flames had not yet been suppressed. Flame cooling is the primary fire extinguishing mechanism; the mass loss rate and combustion heat of the fuel are two key factors. In the other situation, the fire was initially suppressed and subsequently extinguished after a long suppression stage. Surface cooling is the primary fire extinguishing mechanism; the flash point of the fuel is the key factor.     

内拱顶储罐内初始火灾自动灭火系统性能试验研究

为及时有效地抑制石油储罐内发生火灾后的初始火焰,防止火势蔓延后造成更为严重的连锁爆炸事故,研发1种由火灾快速探测系统和快速喷粉系统组成的快速灭火系统,并通过进行性能试验对此系统在石油储罐内的灭火效果进行验证。结果表明:火焰探测系统在探测器距火焰5 m范围内检验并输出报警信号的时间小于50 ms;快速喷粉装置在装粉量为5 kg时,可在310 ms内完成阀门开启至喷粉结束的整个过程。灭火系统可快速检测到火焰并使灭火剂快速有效地达到灭火点,避免火灾发生,具有一定工程应用价值。     

抑制煤矿瓦斯爆炸传播的新技术设想

基于石油阻火装置对可燃气体爆炸传播的火焰具有淬熄作用,对压力波具有抑制作用,提出将金属丝网、波纹板型等几种结构用于抑制煤矿瓦斯爆炸传播的新思路,填补了阻火器在煤矿中应用的空白,为煤矿阻隔爆技术开拓出新的领域.     

Parametric study of the explosivity of graphite-metals mixtures

The explosivity of dust clouds is greatly influenced by several parameters which depend on the operating conditions, such as the initial turbulence, temperature or ignition energy, but obviously also on the materials composition. In the peculiar case of a mixture of two combustible powders, the physical and chemical properties of both dusts have an impact on the cloud flammability and on its explosivity. Nevertheless, no satisfactory ‘mixing laws’ predicting the mixture behavior are currently available and the composition variable to be considered for such models greatly depend on the safety parameters which have to be determined: from volume ratios for some thermal exchanges and ignition phenomena, to surface proportions for some heterogeneous reactions and molar contents for chemical reactions. This study is mainly focused on graphite/magnesium mixtures as they are encountered during the decommissioning activities of UNGG reactors (Natural Uranium Graphite Gas). Due to the different nature and reactivity of both powders, these mixtures offer a wide range of interests. Firstly, the rate-limiting steps for the combustion of graphite are distinct from those of metals (oxygen diffusion or metal vaporization). Secondly, the flame can be thickened by the presence of radiation during metal combustion, whereas this phenomenon is negligible for pure graphite. Finally, the turbulence of the initial dust cloud is modified by the addition of a second powder. In order to assess the explosivity of graphite/magnesium clouds, a parametric study of the effects of storage humidity, particle size distribution, ignition energy, and initial turbulence has been carried out. In particular, it was clearly demonstrated that the turbulence significantly influences the explosion severity by speeding up the rate of heat release on the one hand and the oxygen diffusion through the boundary layer surrounding particles on the other hand. Moreover, it modifies the mean particle size and the spatial dust distribution in the test vessel, impacting the uniformity of the dust cloud. Thus, the present work demonstrates that the procedures developed for standard tests are not sufficient to assess the dust explosivity in industrial conditions and that an extensive parametric study is relevant to figure out the explosive behavior of solid/solid mixtures subjected to variations of operating conditions.     

CO_2分析在含化学添加剂的细水雾灭火研究中的应用探讨

通过实验和计算证明CO2浓度分析是评价含添加剂细水雾灭火有效性的简单而有效方法。采用燃烧分析仪测定细水雾灭火实验过程中的CO2浓度,比较含不同添加剂细水雾和纯水细水雾在同一实验控制条件下的CO2浓度变化规律,利用CO2浓度变化规律判断含添加剂细水雾灭火的效率。根据上述规律,可从两方面比较细水雾的灭火效率:一是CO2的最高浓度。CO2达到的最大浓度小,则燃烧过程中的热释速率小或灭火时间短,说明细水雾抑制燃烧的效果较好。二是施加细水雾后CO2浓度变化率。CO2浓度变化率小,燃烧过程中的热释速率就小,说明细水雾抑制燃烧的效果较好。     

低压下不同新型清洁气体灭火剂抑灭21700型锂离子电池火研究

为探究在航空运输低压环境下Novec1230（全氟己酮）和2-BTP（2-溴-3,3,3三氟丙烯）2种新型清洁气体灭火剂扑灭和抑制空运锂离子电池火的效果,基于动压变温实验舱,自主设计了适用于气体灭火剂的实验灭火装置;在40,60,80 kPa 3种环境压力梯度下开展灭火实验,分析了施加2种灭火剂前后锂电池表面温度变化和灭火过程中的实验现象。结果表明:低压下2-BTP和Novec1230均能有效降低锂离子电池火焰中自由基浓度,快速扑灭明火;2-BTP的降温和抑制温升效果明显优于Novec1230,能更好地抑制锂电池之间的连锁热失控。研究结果可为新一代机载灭火剂的选择提供参考。     

无火源施放后超细微粒灭火剂运动特性研究

超细微粒灭火剂施放后的运动过程直接影响其灭火效果。通过数值模拟及试验研究灭火剂微粒施放后的流动、扩散和沉降等运动特性。模拟结果表明,灭火剂微粒施放后,向下运动到灭火室底部并撞击后向侧壁运动,随后向顶部运动,易在壁面及壁面底角处聚集。试验表明,微粒的运动分喷射运动和沉降扩散2个过程。前者微粒在驱动气流作用下在灭火室顶部、底部及墙壁处积聚,浓度较高。后者微粒主要受重力作用发生沉降,并在湍流气流作用下进行无规则扩散运动,导致灭火室顶部浓度最低;在灭火室垂直方向的一半高度处,浓度较高但波动剧烈;在灭火室底部,当喷射结束后有一个短暂的浓度低谷,随着微粒发生沉降,浓度逐渐升高。喷射压力对灭火剂的运动及浓度分布影响很大,压力过高或过低都会影响灭火剂微粒的全淹没灭火效果。根据试验结果,喷射压力为1.0 MPa时灭火效果较好。     

酒精在常见可燃地面材料燃烧痕迹特征规律研究

易燃液体燃烧痕迹识别对助燃剂放火火灾调查至关重要。选用丙纶地毯和PVC地板革作为纤维和塑料地板的代表,以工业酒精作为易挥发助燃剂的代表,研究酒精用量、灭火方式等对燃烧痕迹形成及痕迹稳定性的影响。通过与未加载酒精的痕迹对比,发现丙纶地毯因热稳定性较差,燃烧后往往能形成烧坑或烧洞,其燃烧轮廓以典型的灰化形式存在,加载酒精的部位熔融严重,与地面紧紧粘连在一起;PVC地板革因为表面光滑,酒精在其表面不断流淌,燃烧后会留下清晰的轮廓,类似于细线状的印痕,而地板革本身基本不会燃烧。燃烧熄灭的方式也会对其炭化程度、燃烧图痕、残余形状产生影响。     

涂装作业场所超细干粉灭火设备设计

涂装作业场所使用的油漆和溶剂一般是易燃易挥发的液体,因而此类场所的火灾爆炸危险很大.一旦发生事故,将会造成巨大的财产和人员损失.本文针对此类场所火灾爆炸事故的特点,分析对比了各种消防系统对此类场所火灾爆炸事故的控制能力,提出了超细干粉灭火系统相对于其他消防系统对于控制此类场所火灾爆炸危险的优点,同时也对探测器的选型进行了讨论,并结合实例进行了超细干粉灭火设备在涂装作业场所的应用设计.