三元组分图在储罐退役惰性化过程设计中的应用

储罐退役之前,一般要进行惰化处理,以降低可燃气体浓度,避免形成爆炸性混合气体。根据三元组分图,可以方便、直观地设计惰化施工的方案,包括惰化操作的程序设计和危险气体控制目标浓度的确定。本文从理论上研究了在储罐退役惰性化过程设计时,如何用三元组分图表示爆炸极限、最小含氧浓度以及在储罐稀释惰性化过程中气体组成的变化轨迹。提出了两套惰化设计方案,在分析比较的基础上,确定了储罐退役惰化时的最安全实施方案。     

Explosion prevention and weighting analysis on the inerting effect of methane via grey entropy model

Explosion prevention is vital for process safety and daily life. In practice, inerting is viewed as an ideal method to reach basic explosion prevention as well as to diminish flammability risk in normal operation, storage, and transportation of materials. This study deals with the inerting effect on the explosion range for methane via grey entropy model, comparatively detected under the different inert gases of nitrogen (N₂), argon (Ar), and carbon dioxide (CO₂), which have various loading inerting concentrations: 10 (90 vol% air), 20 (80 vol% air) and 25 vol% (75 vol% air). The inert influences were determined via the experimental 20-L-apparatus investigations under 1 atm, 30 ^OC, combined with the grey entropy model, which is one of the most prevailingly used grey system theories for weighting analysis and decision-making of the fire and explosion assessment for practical operations. The results indicated that CO₂ had better inerting capacity than the others, as derived from our grey entropy theoretical soft computing calculations. Through the combination of the grey entropy weighting analysis model and the flammability investigations in this study, the concluded decision-making was feasible and useful for the practical applications of inert gases for preventing fire and explosion hazards in relevant processes.     

拱顶储罐气相层惰化过程数值模拟及工艺参数研究

针对油罐在检测、维修前须先将气相层可燃气体用氮气惰化到安全浓度，现场凭经验操作效率低且难以掌握氮气合理用量，容易造成氮气浪费或达不到安全浓度引发事故的问题，为确保惰化过程的安全经济，以常见拱顶储罐为例，首先利用改进后的公式法得出多组分可燃气体惰化效果评价指标；然后根据所得指标采用仿真对储罐气相层惰化过程进行数值模拟，并验证了仿真结果的正确性；最后采用仿真计算方法开展储罐气相层氮气惰化工艺参数的影响研究。研究结果表明:惰化效率与进口压力无关，只随进口流速变化，且大于1 m/s流速后，惰化效率已显著变化，此时可以增加进口管道数量，进一步提高惰化效率。理论研究结果可为现场实施提供参考和指导。     

R290制冷剂惰化燃爆特性实验研究

为了研究R290制冷剂惰化燃爆特性,采用带搅拌功能和氧浓度在线测定的20L球试验装置,对R290制冷剂进行了极限氧浓度测定。实验测定了丙烷在CO2和N2惰化气氛中的爆炸极限及极限空气浓度LAC,确定丙烷的极限氧浓度LOC;采用三元图爆炸区、丙烷-O2二维图爆炸区和ASTM标准分布图分析了混合气体爆炸区边界的燃爆特征,给出了极限氧浓度的确定方法和边界爆炸压力分布规律。实验结果表明:常温常压下R290的爆炸极限为2.1%～9.6%,CO2惰化气氛中的极限氧浓度为13.3%,对应的丙烷浓度为3.3%;N2惰化气氛中的极限氧浓度为10.8%,对应的丙烷浓度为2.7%。通过对比分析不同CO2和N2浓度下的爆炸区分布特征,表明CO2对丙烷的惰化效果要优于N2,以氮气和二氧化氮体积分数比为1∶2测试惰化气氛保护能力,惰化效果介于同浓度单种惰性气体之间。     

Inerting characteristics of ultrafine Mg(OH)2 on starch dust explosion flame propagation

Experiments on the flame propagation of starch dust explosion with the participation of ultrafine Mg(OH)₂ in a vertical duct were conducted to reveal the inerting evolution of explosion processes. Combining the dynamic behaviors of flame propagation, the formation law of gaseous combustion products, and the heat dissipation features of solid inert particles, the inerting mechanism of explosion flame propagation is discussed. Results indicate that the ultrafine of Mg(OH)₂ powders can cause the agglomeration of suspended dust clouds, which makes the flame combustion reaction zone fragmented and forms multiple small flame regions. The flame reaction zone presents non-homogeneous insufficient combustion, which leads to the obstruction of the explosion flame propagation process and the obvious pulsation propagation phenomenon. As the proportion of ultrafine Mg(OH)₂ increases, flame speed, flame luminescence intensity, flame temperature and deflagration pressure all show different degrees of inerting behavior. The addition of ultrafine Mg(OH)₂ not only causes partial inerting on the explosion flame, but also the heat dissipation of solid inert particles affects the acceleration of its propagation. The explosion flame propagation is inhibited by the synergistic effect of inert gas-solid phase, which attenuates the risk of starch explosion. The gas-solid synergistic inerting mechanism of starch explosion flame propagation by ultrafine Mg(OH)₂ is further revealed.     

Explosion hazards related to hydrogen releases in nuclear facilities

Hydrogen explosion risk needs to be carefully assessed and evaluated in nuclear facilities because of the potential catastrophic consequences: breakdown of safety equipments, failure of containment, dissemination of radioactive materials in the environment.When studying an indoor release, one possible simplification is to assume a perfect gas mixing inside the room. This assumption is effectively often used to evaluate toxic risks in the environment outside a building (Mastellone, Ponte, & Arena, 2003). However, perfect gas mixing assumption is only a rough approximation, as indoor concentrations can largely differ from mean values, due to buoyancy, recirculation zones or obstacles for example.In order to better evaluate the risk of explosion in case of an accidental release of hydrogen, IRSN conducted a numerical study using FLACS CFD software. Several parameters have been studied to identify dangerous situations and draw a representative picture of the risk: room size, position and direction of hydrogen leak, ventilation characteristics. Hydrogen release flow rates used for numerical simulations have been chosen as the highest leak rate which, by applying the assumption of perfect mixing, produces an average concentration in the room equal to hydrogen lower flammability limit (LFL).Simulation results indicate that in some particular configurations, especially for impinging hydrogen jets, hydrogen concentrations can locally be above LFL and then create explosive atmospheres with significant volumes.     

Experimental investigation of the influence of inert solids on ignition sensitivity of organic powders

This work presents the results of the experimental characterization of the ignition sensitivity of solid inertant/combustible powders mixtures. Three inert solids (alumina, Kieselguhr, aerosil) and eleven organic powders have been considered and the following parameters have been determined: (1) the minimum ignition energy, (2) the minimum ignition temperature in cloud and (3) the minimum ignition temperature in 5 mm layer. The effects of the addition of inert solids are described and a simple model is proposed to represent the experimental results.Generally, increasing inert solid content in a powder leads to a higher minimum ignition energy as well as a higher minimum ignition temperatures in cloud and in layer. In some cases, the flammability is influenced above a threshold concentration value, which can be quite high (up to 85 wt.%). Indeed, the proposed model shows a zone below the minimum ignition concentration (MIC), which does not enable an efficient or safe inerting: either the admixed inert solid does not provide a sufficient effect, or it can even facilitate the ignition of the dust by notably improving its dispersability.The influence of key parameters such as the thermal conductivity or optical properties on the efficiency of the inerting by admixed solid need to be further assessed in a future work in view to better understand the mechanisms involved and to extend the scope to other types of oxidizable materials.     

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.     

Optimization of recertification intervals for PSV based on major accident risk

Overpressure is a major hazard in the process industry with the potential to lead to a major accident. Pressure Safety Valves (PSVs) are often used as the last layer of protection against such a hazard and require regular recertification in order to be dependable. The valve safely vents gas from a vessel when the pressure becomes excessive. It is often the practice in industry to apply one or two years as the normal recertification interval of PSV. However, experience from the Norwegian oil and gas industry is that the recertification process several times have caused leaks of gas. The process thus represents a certain risk in itself and the question is then whether the recertification intervals presently being used actually are optimal from a risk point of view? The objective of this paper is to look into this problem, applying typical data from an oil and gas installation. An optimal recertification interval will be calculated based on minimization of risk to personnel.     

Application of CREAM human reliability model to cargo loading process of LPG tankers

The storage and handling processes of liquefied petroleum gas (LPG) constitutes a complex operational environment in the maritime mode of transportation. The LPG cargo is carried by specially designed ships called LPG tankers. The LPG cargo loading and discharging operations have always potential hazards. Thus, the crew on-board LPG tankers should be fully aware of operational risks during the cargo handling process, which includes various critical tasks such as drying, inerting, gassing-up, cooling, and reliquefaction. During these stages, human reliability (operation without failure) plays a crucial role in sustainable transportation of cargo. Human reliability analysis (HRA), related to various parameters such as the human factor, technology, and ergonomics, is always a critical consideration as regards maritime safety and environment. The main focus of the research is to systematically predict human error potentials for designated tasks and to determine the required safety control levels on-board LPG ships. The paper adopted CREAM (Cognitive reliability and error analysis method) basic and extended versions in order to assess human reliability along with the cargo loading process on-board LPG tanker ships. Specifically, the model is demonstrated with an operational case study. Consequently, the research provides should contribute to maritime safety at sea and prevention of human injury and loss of life on-board LPG ship.     

Experiment-based investigations of magnesium dust explosion characteristics

An experimental investigation was carried out on magnesium dust explosions. Tests of explosion severity, flammability limit and solid inerting were conducted thanks to the Siwek 20 L vessel and influences of dust concentration, particle size, ignition energy, initial pressure and added inertant were taken into account. That magnesium dust is more of an explosion hazard than coal dust is confirmed and quantified by contrastive investigation. The Chinese procedure GB/T 16425 is overly conservative for LEL determination while EN 14034-3 yields realistic LEL data. It is also suggested that 2000-5000 J is the most appropriate ignition energy to use in the LEL determination of magnesium dusts, using the 20 L vessel. It is essential to point out that the overdriving phenomenon usually occurs for carbonaceous and less volatile metal materials is not notable for magnesium dusts. Trends of faster burning velocity and more efficient and adiabatic flame propagation are associated with fuel-rich dust clouds, smaller particles and hyperbaric conditions. Moreover, Inerting effectiveness of CaCO₃ appears to be higher than KCl values on thermodynamics, whereas KCl represents higher effectiveness upon kinetics. Finer inertant shows better inerting effectiveness.     

Minimum Ignition Temperature of layer and cloud dust mixtures

The prevention of dust explosions is still a challenge for the process industry. Ignition, in particular, is a phenomenon that is still not completely understood. As a consequence, safety conditions pertaining to ignition suppression are rarely identified to an adequate level. It is well known that, in general, the ignition attitude of a dust depends on several factors, such as the nature of the chemical, the particle size, moisture content, etc., but there is still a lack of knowledge on the effect of the single variables.This paper has the aim of providing data on the Minimum Ignition Temperatures of dust mixtures obtained from a mixing of a combustible dust (flour, lactose, sucrose, sulphur) and an inert dust (limestone, extinguishing powders) as well as from the mixing of two different combustible dusts. Various mixtures with different weight ratios have been tested in a Godbert Greenwald (GG) furnace and on a hot plate in order to measure the effect of mixture composition on the Minimum Ignition Temperature (MIT_L) of the layer and on the Minimum Ignition Temperature (MIT_C) of the cloud. In order to further verify the effects of inert dust particle size, inerts sieved to different size ranges have been tested separately. Generally, both MIT_L and MIT_C increase as the inert content is increased. MIT_C is poorly affected by inert particle size when limestone is used. The MIT_L of pure flour is higher than the MIT_L of mixtures containing up to 40% of 32–75 μm of limestone. This was probably due to the behaviour of pure flour during the test, which demonstrated strong tendency to produce char, cracks in the layer and detachment from the hot plate.     

Quantitative evaluation of precautions on chemical tanker operations

Large quantities of liquid chemicals are carried by chemical tankers all over seas. Chemical cargoes have different properties and chemical tankers are complex ships that are designed to carry different types of chemical cargoes. Carriage of chemical cargoes contains different hazards both for human life and marine environment. There are several cargo operations that are regularly done on chemical tankers such as loading, discharging, inerting, washing tanks, sampling, and freeing gas. These operations constitute their own risks. Therefore, risk assessment has become a critical issue in maritime industry. The present investigation of this study is attempting to examine the priorities of precautions that are taken by chemical tankers before, during, and after cargo operations. Analytic hierarchy process (AHP) is used for prioritizing the precautions in order to clarify the risk assesment option that will be used for pro-active approach to prevent marine casualties. The main aim of this study is to identify an appropriate management tool to increase the level of safety for chemical tankers during cargo operations at a terminal by using the results of AHP application.     

受限空间内惰性气体对CH4爆炸抑制特性研究

N2和CO2是常用的惰性抑爆气体,为研究两种气体的抑爆特性,采用20L球形爆炸试验装置,分析了不同浓度配比条件下N2/CH4/空气以及CO2/CH4/空气混合气体的爆炸压力,同时采集爆炸后的气体样品,对比分析爆炸后残留气体的主要成分。结果显示:随CH4浓度从5%增加至12.5%时,完全抑制CH4爆炸需要的惰性气体最小量先增大后降低,CH4浓度在6.5%~7.5%之间时,抑爆需要的惰性气体的量最大;在同一CH4浓度条件下,抑爆需要N2的量大于CO2,并且CH4浓度在5%~6.5%时,抑爆需要两种惰性气体的量值差别最大;当CH4浓度一定时,随着加入惰性气体量的增大,爆炸最大超压逐渐降低,惰性气体浓度和爆炸超压之间基本呈线性关系;在同样条件下,相对于N2,CO2为抑爆气体时,爆炸后腔体内残留的CH4浓度较高。研究成果为惰性气体抑爆技术提供技术支撑,同时为揭示惰性气体抑爆机理有一定作用。     

Fire-Extinguishing Effectiveness of 1-Bromo-3,3,3-Trifluoropropene/Inert Gaseous Mixture Evaluated by Cup Burner Method

1-bromo-3,3,3-trifluoropropene with low extinguishing concentration has been identified, but it has high boiling points and is not suitable replacements for halon 1301. However, mixtures of 1-bromo-3,3,3-trifluoropropene in an inert gas could produce fire-extinguishing agents with many of the desirable properties of halon 1301. To study binary fire suppressants, one has to determine the extinguishing concentration of the 1-bromo-3,3,3-trifluoropropene/inert gas mixtures. In this study, a method based on cup-burner was used to estimate the extinguishing concentration of 1-bromo-3,3,3-trifluoropropene/inert gas mixtures. A mechanism for mixing 1-bromo-3,3,3-trifluoropropene with inert gas before applying to fire was proposed. The results show that addition of small amount of 1-bromo-3,3,3-trifluoropropene in inert gas reduces the extinguishing concentration of inert gas considerably, and 1-bromo-3,3,3-trifluoropropene/inert gas mixture suppressant shows strong synergistic interactions at low mole concentration of 1-bromo-3,3,3-trifluoropropene.     

煤矿安全隐患动态分级闭环管理方法及应用

为了治理煤矿生产过程中的安全隐患,遏制煤矿安全生产事故,对煤矿生产过程中的安全隐患管理进行了研究。经过梳理国内外相关文献,辨析了煤矿危险源和安全隐患的关系;结合脆弱性分析了煤矿安全隐患的风险大小,结合LEC法说明了安全隐患风险分级标准;结合煤矿生产过程的特点,提出了煤矿安全隐患动态分级闭环管理方法,设计了与之配套的奖惩办法。煤矿安全隐患动态分级闭环管理方法和配套的奖惩办法在南方的一个千万吨级矿井进行了应用。研究表明,该方法可以有效提高煤矿安全隐患的治理能力,提高煤矿现场的安全管理水平。     

油页岩利用过程粉尘爆炸研究现状及趋势分析

在石油资源日益紧张的形势下,我国油页岩资源的开发利用正得到前所未有的重视,但其利用过程潜在的粉尘爆炸危险性并未引起关注。对国内外有关油页岩粉尘着火、爆炸的文献进行了综述,约旦学者对油页岩粉尘爆炸下限、着火温度及惰化粉尘对下限的影响进行了持续性的研究。国内学者多涉及油页岩利用工艺的研究,只注重页岩油蒸气的爆炸风险,多采用经验公式的方法进行分析,具有较大的局限性。根据爆炸风险控制原理,提出了油页岩粉尘防爆安全需要进一步进行的基础研究工作,突出了加强油页岩粉尘和蒸气杂混物爆炸机理研究的重要性。     

Integrating cybersecurity in hazard and risk analyses

As operational and information technologies converge to allow for remote and real-time access to plant operating data and control functions, the process industry could become increasingly susceptible to cyber-attacks. Traditional hazard and risk analysis methods appear inadequate to identify, prevent, and mitigate such attacks. This paper discusses the significance of incorporating cybersecurity vulnerability analysis not just as part of process hazard analysis (PHA), but also in terms of protecting the process control network and implementing adequate safeguards in general against cyber threats. A layer of protection analysis (LOPA) is adapted to evaluate potential weaknesses and ensure safeguards for critical applications would be resistant to cyber-attacks. Integrating cybersecurity into hazard and risk analyses as well as other elements of process safety management (PSM) is demonstrated with examples, making the plant more resilient against both traditional and cyber threats.     

都汶公路高瓦斯隧道施工火源控制关键技术研究

安全控制是高瓦斯隧道监理工作的核心控制内容之一。都（江堰）汶（川）公路高瓦斯隧道断面大,施工倍受瓦斯危害困扰,安全控制难度巨大。而火源则是大断面隧道施工中引起瓦斯燃烧或爆炸的导火索,因而如何遏制火源便成为监理单位抓好安全控制的一大重点。但目前尚无具体先例、方法可循,相关隧道施工规范、监理规范也未对此作出明确的规定。文章通过都汶公路紫坪铺（原名董家山）隧道2005年“12·22”特大瓦斯爆炸事故后的火源监控工作实践,总结出了一套火源监控对策,这对今后类似高瓦斯隧道施工火源控制和推动安全监理技术进步具备较大的借鉴价值。     

Solid inertants and their use in dust explosion prevention and mitigation

This paper is a review of the use of inert dusts to reduce the risk of dust explosions through both prevention and mitigation schemes. The review is conducted by referring primarily to the research results of the author and his colleagues in this area, with appropriate reference to the work of other researchers. A functional distinction is first made between inerting and suppression by explaining each term within the contexts of explosion prevention and explosion mitigation, respectively. The use of solid inertants is then described in terms of the various inhibitor and situation-specific parameters that can influence their effectiveness. Finally, application examples of the research results are given for research laboratories, test facilities, design engineers, and industrial practitioners.