Remote extinguishing of large fires with powder aerosols

A new method for distant extinguishing of fire spreading in an extended closed volume such as a mine working, storehouse, subway tunnel, electric cable channels, etc. is proposed. A novel extinguishing agent based on a stable mixture of superfine ammonium phosphate [NH₄H₂PO₄] and modified fumed silica [SiO₂–CH₃] is supplied to the fire by a powerful ventilator. The properties of the extinguishing agent (average particle size, airborne residence time, distance of transfer by the air stream) have been studied in an experimental chamber (100 m³). A test extinguishing of a large‐scale fire has been performed in an experimental tunnel 180 m in length. Extinguishing agent consumption, dynamics of temperature change over the tunnel length and composition of fire gases were recorded in this test. The influence of foam concentration, addition of nitrogen and halons to aerosol, were also studied. Copyright © 2006 John Wiley & Sons, Ltd.     

Fire suppression performance of a new type of composite superfine dry powder

To enhance the performance of existing dry powders and ensure process security, a new type of dry powder based on ammonium dihydrogen phosphate (NH₄H₂PO₄) was prepared. The prepared composite superfine dry powder was denoted as NH₄H₂PO₄/zeolite composite in this paper. The effectiveness of commercial ABC dry powder, superfine dry powder, and the NH₄H₂PO₄/zeolite composite in fire suppression were compared in a small‐sized fire‐extinguishing chamber. Laboratory‐scale tests showed that the NH₄H₂PO₄/zeolite composite had considerably superior fire‐extinguishing efficiency to that of commercial ABC dry powder and superfine dry powder, along with shorter average extinguishing time and less average mass of powders consumed. In addition, the NH₄H₂PO₄/zeolite composite also displayed much improved toxic gas suppression ability. The physical and chemical characteristics of commercial ABC dry powder, superfine dry powder, and the NH₄H₂PO₄/zeolite composite were characterized using a range of techniques of laser particle size analysis, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. Based on the analysis results, the improved fire suppression performance of the NH₄H₂PO₄/zeolite composite can be ascribed to smaller particle size, larger surface area, and a special chemical decomposition process.     

Studies of fundamental physical–chemical mechanisms and processes of flame extinguishing by powder aerosols

Theoretical and experimental studies on mechanisms of interaction of the fire‐extinguishing aerosol with flame are carried out. The factors of heterogeneous inhibition of flame free radicals (O, OH, H, CH_x) on a crystal surface of inorganic salts being the basic components of fire‐extinguishing powders and aerosols are measured using laboratory equipment. The semi‐empirical calculations by methods of quantum chemistry for heterogeneous and homogeneous inhibition reactions of burning are executed. The thermal mechanism for fire extinguishing is evaluated. The universal mechanism of influence on flame of a crystal surface of a fire‐extinguishing powder particle is offered. Copyright © 2007 John Wiley & Sons, Ltd.     

化学组分对干水灭火剂流动性与保水性的影响

干水（dry water）是微水滴颗粒被纳米级疏水性二氧化硅颗粒包覆层封装形成的、整体呈固体粉末状的粉体材料,其颗粒内含水量可高达98%,内部水分可以通过高温蒸发和外力挤压作用释放出来,是很有潜力的特种灭火新型材料。干水灭火剂的核心是功能性化学灭火组分,本文设计并制备了包覆不同功能性化学灭火组分的系列干水灭火剂,并测定表征了所制备干水灭火剂的粒径分布、流动性与保水性,研究了不同功能性化学灭火组分对干水灭火剂储运性能的影响。结果表明,不同功能性化学灭火组分的加入能够在一定程度上提高干水材料颗粒的流动性和保水性,其中磷酸二氢铵干水的流动性最优,氯化钠干水的保水效果最好。研究对干水灭火剂的制备、储运与使用具有重要意义。     

常用灭火剂灭火性能及原理

详细介绍了气体灭火剂、泡沫灭火剂、干粉灭火剂和气溶胶灭火剂等多种常用灭火剂的性能及灭火原理,并对其适用条件进行了说明。     

A novel hot aerosol extinguishing agent with high efficiency for Class B fires

A novel hot aerosol extinguishing agent (HAEA), which is the combination of pyrotechnics and flame retardant technology, was found to have great efficiency in extinguishing Class B fires. A mixture of P and P₃N₅, referred to as P90x, was chosen as the reductant, and phase stabilized ammonium nitrate was chosen as the oxidant. This paper describes a study of the effectiveness of this agent in extinguishing n‐heptane fires (ie, Class B fires). We determined that the best efficiency was 15 g/m³ for extinguishing n‐heptane fires, four times more efficient than a traditional agent. The efficiency increases as the mass fraction of P90x rises. We also identified the key difference between the novel extinguishing agent and the traditional agent. The former consists of an inorganic phosphorus compound, while the latter is mainly comprised of KOH. Consequently, their extinguishing mechanisms are different. The phosphorus oxide of the novel HAEAs is the leading component to extinguish fire, which is more effective than alkali salts.     

蛭石粉末及离子溶液改性后膨胀率和灭火有效性分析

为了研发高效干粉灭火剂粉体,提升干粉灭火剂的灭火效果,本文以蛭石粉为研究对象,采用NaCl、NaHCO₃、MgCl₂和KCl四类离子溶液对不同粒径的蛭石粉进行改性处理,并分析了原始蛭石粉末以及改性后的蛭石粉的膨胀率和表面微观结构。随后开展了ABC干粉灭火剂、未改性蛭石粉、MgCl₂改性蛭石粉、NaCl改性蛭石粉、KCl改性蛭石粉、NaHCO₃改性蛭石粉扑灭油池火实验,分析了灭火时间、灭火剂用量以及复燃情况。研究结果表明：粒径150 μm的蛭石粉末膨胀率最大,且经过改性的蛭石粉末的膨胀率要明显大于原始蛭石粉末,其中MgCl₂改性后的蛭石粉膨胀率最大,接近2.4左右;从灭火时间来看,灭火效果从低到高依次为ABC干粉灭火剂、未改性蛭石粉、MgCl₂改性蛭石粉、NaCl改性蛭石粉、KCl改性蛭石粉、NaHCO₃改性蛭石粉;从灭火剂用量角度可得出：改性蛭石粉灭火用量要明显小于未改性蛭石粉。其中,NaHCO₃改性蛭石粉用量与ABC干粉灭火剂用量相对接近。从复燃角度来看,膨胀蛭石粉末的密度较小,可长时间悬浮在油品表面,有效阻止复燃,效果明显优于传统的ABC类干粉灭火剂。     

热、冷气溶胶灭火技术在汽车固定式灭火装置上的应用

简单介绍了气溶胶灭火剂的灭火机理、分类及应用现状,分析了汽车火灾的原因,着重探讨了两种新型汽车用固定式灭火装置即热气溶胶灭火装置与超细干粉灭火装置之间制备、性能等方面的区别,展望了热气溶胶产品在汽车火灾方面的应用前景.     

Experimental assessment on LPG fire extinguishing properties of three chemical powders before and after milling action

The extinguishing performance of three dry chemical powders (DCPs) was investigated through a lab-scale suppression system for liquefied petroleum gas (LPG) fire. The magnesium hydroxide (Mg(OH)₂ ), sodium bicarbonate (NaHCO3 ), and commercial ABC − MAP powders are used to prepare two groups of samples: raw samples and milled samples. The effect of milling action on the properties of DCPs, such as the bulk density, microstructure, particle size, thermal decomposition, and the extinguishing performance, is analyzed. The density test revealed that the bulk density increased after milling, and the Mg(OH)₂ had a lower density than the other powders. The microstructure analysis showed that the milled powders had a smaller particle size and more regular shapes than raw powders. The thermal analysis demonstrated that the powder decomposition process was somewhat similar with a slight difference in initial decomposition temperature and degradation rate. The fire tests proved that the extinguishing efficacy greatly improved after the samples were milled. Moreover, the experiments indicated that the milled Mg(OH)₂ was superior in fire extinguishing to the other samples with shorter extinction time and less agent quantity consumed. Based on the results, it can be inferred that the milling action has a significant influence in enhancing the extinguishing mechanisms' efficiency of DCPs.     

Fire suppressing performance of superfine potassium bicarbonate powder

Fire suppression effectiveness of a new kind of dry powder based on potassium bicarbonate was studied in this paper. The powder consisted of superfine potassium bicarbonate and some organic and inorganic additives, which was denoted as ‘K‐powder’. The physical and chemical characteristics of the K‐powder were characterized by a series of techniques of X‐ray diffraction, scanning electron microscopy, Fourier transforms infrared (FTIR) and thermal gravity analysis, etc. Performance of the new potassium‐based powder in fire suppression was studied by laboratory‐scale experiments, which exhibited much superior fire suppression efficacy than that of the commercial bicarbonate powder. Such improvements could be reasonably ascribed to the special chemical composition, microstructure and radiation effect on the mechanisms. The preparation, fire suppression and possible fire‐extinguishing mechanisms were studied in detail. Copyright © 2010 John Wiley & Sons, Ltd.     

超细磷酸铵盐干粉灭火剂研究

对Halon灭火剂的最佳替代品磷酸铵盐干粉灭火剂进行了研究。采用超音速气流粉碎机和特殊的表面处理方法对磷酸铵盐干粉进行超细化和硅化处理,制备出了平均粒径为7 28μm、比表面积为1 80m2/cm3的超细磷酸铵盐系列干粉灭火剂。用疏水保持率、吸湿率、抗结块性等指标对磷酸铵盐干粉灭火剂的主要性能进行了表征。灭火效果对比实验结果表明,超细化后的磷酸铵盐干粉灭火剂有效灭火次数由原来的2次增加到6次,有效灭火时间由原来的4s缩短到1s,其灭火效能约为普通型的4倍。     

Effect of particle size on the properties of Mg(OH)2‐filled rubber composites

A novel nanomagnesium hydroxide powder and three kinds of micro‐Mg(OH)₂, with different particle sizes, were chosen as fillers and mixed with ethylene–propylene–diene monomer rubber (EPDM) to form a series of composites by a traditional rubber‐processing technique. The results showed that the mechanical properties of composites improved with decreasing particle size. The nanocomposites were far stronger than the microcomposites, which also supported the view that rubber reinforcement requires nanoreinforcement. The effect of particle size on the fire resistance of composites was investigated by cone calorimetry and limiting oxygen index analysis, which showed that the particle size of powder had an impact on the fire resistance of composites. For the composites filled with untreated powder, the peak value of heat release rate decreased and T_ign increased with decreasing particle size. In conclusion, the fire resistance of nanocomposites was better than that of microcomposites. Surface modification of particles sometimes substantially improved the mechanical properties of nanocomposites, but had no effect on either the mechanical properties of microcomposites or the fire resistance of nanocomposites and flame retardance. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2341–2346, 2004     

D类干粉灭火系统在烷基铝类化学品消防中的应用

对烷基铝类火灾的特点与灭火剂种类选择等进行了分析,结合异戊橡胶装置中烷基铝类催化剂配制区固定干粉灭火系统的消防保护工程设计实例,从D类干粉灭火系统原理、系统设计、系统组成等几个方面进行了较为详细的阐述,期望为今后类似工程的消防设计提供经验和指导。     

An efficient methodology for evaluating the nozzle performance of water-based automatic fire extinguishers

The performance of automatic fire extinguishers (AFE) was tested using a novel nozzle distribution test in relation to a point of visual approach. The visual nozzle distribution data was obtained from the mapping of the amount of the collected fire extinguishing agent to each position and the gradient was given in accordance with the visually collected amount. The results showed that the effective discharge time was determined by the nozzle structure and its size. The visual nozzle distribution test (VNDT) provided relevant information regarding the performance efficiency of AFE, including the nozzle coverage area, the effective amount of the fire extinguishing agent and the distribution uniformity of fire extinguishing agents, and calculations for the proper amount of a fire extinguishing agent to extinguish a fire. Consequently, the results indicate the VNDT is an excellent method for analyzing the performance efficiency of AFE.     

泡沫灭火剂中全氟辛烷磺酸类物质的管控行为及替代物研究进展

全氟辛烷磺酸（perfluorooctane sulfonic acid, PFOS）使水成膜泡沫灭火剂（aqueous film forming foam,AFFF）具有较好的耐高温和抗烧能力,但由于PFOS的难降解性、生物富集性及毒性,国内外相继对PFOS类物质进行了管控。本文简述和分析了泡沫灭火剂中PFOS类物质的管控行为及替代物研究,分析表明管控行动逐步从限制走向淘汰,研究泡沫灭火剂中PFOS类物质的替代物极为迫切;替代物的研究方向主要有两个,一个是泡沫灭火剂中短氟碳链类表面活性剂研究及短氟碳链泡沫灭火剂的灭火效果验证,但短氟碳链类表面活性剂可能存在长期环境持久性的问题;另一个是泡沫灭火剂中无氟类表面活性剂的研究,如有机硅表面活性剂、甜菜碱型表面活性剂、纯化皂苷表面活性剂,但无氟类表面活性剂可能会影响无氟泡沫灭火剂的表面活性、灭火能力、灭火效果等。泡沫灭火剂中PFOS类物质的替代物研发尚任重而道远。     

空气泡沫灭火剂与石油化工火灾扑救

近年来频发的石油化工火灾为人们敲响了安全警钟,再一次引起人们对石油化工火灾问题的高度关注。文章介绍了在石油化工火灾中常用空气泡沫灭火剂的种类、灭火机理、适用范围、优点及不足,指出了空气泡沫灭火剂使用时的注意事项,并展望了其在石油化工火灾中的应用前景。     

Effect of expandable graphite particle size on the flame retardant,mechanical, and thermal properties of water‐blown semi‐rigid polyurethane foam

Different particle size of expandable graphite (EG) were incorporated into water‐blown semi‐rigid polyurethane foams (SPFs), which acted as the fire shield, in order to enhance the fire retardant properties. In this study, the particle size of EG was systematically varied from 70 µm to 960 µm. The effect of EG particle size on the density, mechanical properties, and thermal stability of SPFs was also investigated. Results showed that EG with smaller particle size showed almost no effect on the fire retardant properties of SPFs while the larger particle size of EG could effectively enhance it. It was observed that the flame retardancy of the composite improved with the increase of EG size which was attribute to the formation and densification of isolation layer with the increase in volume of expanded graphite. Limiting oxygen index (LOI) value of EG/SPF composites increased linearly by two steps with the increase in EG particle size. Horizontal burning test confirmed the above conclusion. Thermogravimetric analysis (TGA) indicated that EG particles and its size exhibited minor effect on the thermal stability of the SPF composites. Moreover, SPF filled with medium particle size of EG (about 400 µm) exhibited a poor compression performance compared with the others. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39885.     

Performance evaluation of bromofluoropropene in extinguishing liquid fuel spray fires

Liquid fuel spray fires emit high radiation heat fluxes, posing great threat to humans. The study of suitable agents and techniques for extinguishing this particular type of fire is of great importance. In this study, degradable 2‐bromo‐3,3,3‐trifluoropropene (BTP), a new clean fire extinguishing agent, was tested for its effectiveness in extinguishing three types of liquid fuel spray fires, namely diesel, gasoline, and ethanol. Bench‐scale experiments were conducted in a 6 × 5 × 3 m compartment with natural ventilation. The liquid fuels sprayed at varying pressures were ignited by a small open flame and then extinguished by a portable BTP extinguisher. Results showed that BTP of less than 60.0 g could extinguish all liquid fuel spray fires of 0.20 to 1.0 MPa in less than 2.0 s. The results also showed that when compared with fire sparked by gasoline and diesel, it is significantly easier to put out ethanol spray fires because of its high flame temperature and low flame power. Based on well‐established fire suppression theories and experimental results, the detailed mechanism of how BTP functions as an extinguishing agent in the suppression of liquid fuel spray fires will be discussed. Copyright © 2013 John Wiley & Sons, Ltd.     

Evaluation of small scale n-heptane fire extinguishing efficacy by natural antioxidants based pyrotechnic compositions: An experimental study

The conventional pyrotechnic compositions (PCs) for firefighting application mostly consist of potassium nitrate, chlorate or perchlorate as oxidants and organic resin-like phenol-formaldehyde, melamine-formaldehyde, epoxy resin and polyurethanes are used as reducers. Unfortunately, there are also some potential disadvantages to the use of conventional compositions. These are related to high combustion temperature with the generation of heat and flame which may cause secondary fire chances and hazards associated with the use of organic resins. Exposure to phenol, melamine, epoxy resins and polyurethanes are considered as a life-threatening occupational hazard. Under the present study, new pyrotechnic compositions were prepared with the combination of natural antioxidants like ascorbic acid and gallic acid as reductant and mixture of potassium nitrate with potassium chlorate as oxidant. Fire extinguishing efficacies, calorific value, burn rate, the flame temperature of newly developed compositions was evaluated against potassium nitrate and phenol-formaldehyde resin-based conventional composition. Although both the new and conventional composition has shown good fire extinguishing efficacies, extinguishing 4.57 KW of small scale n-heptane pool fire in 3 to 4 seconds, these newly developed compositions showed 67% to 76% reduction in flame temperature. It was also found that these new compositions exhibit a faster burn rate and lower calorific value than the conventional composition. To understand the fire extinguishing mechanism by the discharged aerosol particulate, its physical and chemical characteristics were assessed by a series of techniques viz; HRXRD, SEM, FTIR, EDX.     

EBM气溶胶灭火剂产物的潮解研究

EBM气溶胶灭火剂是一种新型高效灭火剂,其灭火效率高于哈龙类灭火剂。燃烧反应产生的白色烟雾对火灾具有抑制作用。白色烟雾中含有固体颗粒物质,这些颗粒物降落形成的残留物潮解后对金属材料及线路板等有腐蚀性。对气溶胶灭火剂颗粒物潮解进行研究,研究结果表明:空气的相对湿度是影响气溶胶颗粒物潮解的主要因素。