Some aspects in testing and assessment of metal dust explosions

The dust explosion committee of the Association of Powder Process Industry and Engineering, Japan recently established two testing standards for dust explosions. In the investigations for the standardization, many experimental data have been obtained for the dusts currently used in Japanese industries. Data for zirconium, tantalum and silicone dusts are presented to discuss the use of test methods, which have been accepted internationally. The test methods for dust explosions have to consider a variety of kinds and forms of dusts to be tested.     

新桥硫铁矿露天采场一期工程爆破的安全管理

新桥硫铁矿加强爆破安全管理工作，实现了15年无爆破事故。     

Temperature profile across the combustion zone propagating through an iron particle cloud

Knowledge of the mechanism of combustion zone propagation during dust explosion is of great importance to prevent damage caused by accidental dust explosions. In this study, the temperature profile across the combustion zone propagating through an iron particle cloud is measured experimentally by a thermocouple to elucidate the propagation mechanism. The measured temperature starts to increase slowly at a position about 5 mm ahead of the leading edge of the combustion zone, increases quickly at a position about 3 mm ahead of the leading edge, reaches a maximum value near the end of the combustion zone, and then decreases. As the iron particle concentration increases, the maximum temperature increases at lower concentration, takes a maximum value, and then decreases at higher concentration. The relation between the propagation velocity of the combustion zone and the maximum temperature is also examined. It is found that the propagation velocity has a linear relationship with the maximum temperature. This result suggests that the conductive heat transfer is dominant in the propagation process of the combustion zone through an iron particle cloud.     

Towards an inherently safer bioprocessing industry: A review

The bioprocessing industry is regarded as one of the fastest growing sectors with an estimated compound annual growth rate of 8.6%. The global market for biopharmaceuticals is projected to rise to a market value of USD 727.1 billion by 2025. Due to the unique nature of bioprocessing industries wherein micro-organisms are employed to manufacture the desired products, these processes are prone to additional hazards such as biological hazards and dust explosion amongst others. This necessitates the need to review the existing research in the fields of biotechnology and bioprocessing to reduce/eliminate these hazards and pave the path towards a safer bioprocessing industry. The study involves developing a framework comprising of studying the recent technologies that reduce/eliminate these hazards involved in the bioprocessing industries that include dust explosions, loss of containment of toxic chemicals, loss of containment of biohazard/active product ingredient, fire, and explosion and mapping these technologies with respect to inherent safety principles that include substitution, minimization, moderation and simplification with an overall objective of minimizing the risk associated with bioprocesses and moving towards an inherently safer bioprocessing industry.     

Consequence analysis of premixed flammable gas explosion occurring in pipe using a coupled fluid-structure-fracture approach

A coupled fluid-structure-fracture approach incorporating a high-efficiency detonation modeling algorithm was proposed to study the consequences of premixed flammable gas explosion occurring in pipe. A strain-rate-dependent failure criterion which is the vital prerequisite for accurate consequences prediction was derived based on the failure mechanism of materials at high strain rates and it was applied to account for the fracture of pipe. The simulated pressure time history and fracture patterns were validated against experimental results and good agreements were acquired. The interaction between detonation wave and pipe during crack extension, dynamic fracture processes of pipes with different initial flaws, venting features of detonation products and pressure profiles out of pipe were obtained and discussed in detail. The comparison with existing semi-empirical and CFD methods was performed and it is revealed that the deformation and fracture of pipe have obvious negative influences on the peak overpressure and the rate of pressure increase out of pipe. Because the energy absorption and dissipation due to structural deformation and fracture are well taken into account, the coupled fluid-structure-fracture method is expected to provide more rational consequences prediction and analysis results.     

地铁屏蔽门安全系统分析及改进

地铁屏蔽门夹人事故时有发生,对其事故树进行分析获得导致事故发生的基本事件重要度排序,结果表明,安全系统与警示装置的不完善是造成事故的主要因素。由此提出对红外探测系统和警示灯系统进行改进以减少地铁屏蔽门事故。     

柱形连通容器内预混气体爆炸过程的火焰传播模拟

为研究连通容器内气体爆炸规律,采用Fluent(经典流体动力学软件)对柱形连通容器内预混气体爆炸过程进行模拟,模拟了不同点火位置和火焰传播方向条件下连通容器内火焰传播过程和压力变化,并分析了连通容器内不同时刻的速度场.结果表明:火焰面在传播过程中并非完全对称,当火焰到达传爆容器后,湍流燃烧剧烈,火焰不规则变形显著;端面点火后在传爆容器内产生的压力峰值和压力波动比中心点火时更大;当起爆容器为大容器时,传爆容器内气体预压缩程度更大,压力峰值更高.     

锂离子电池过充爆炸强度试验研究

过充是导致电池爆炸的一种常见原因,分析过充与电池爆炸的关系及过充所导致的电池爆炸对周围环境的破坏程度极其重要.以10 Ah三元材料锂离子电池为研究对象,采用不同倍率过充方式刺激锂离子电池,利用高速摄影仪、红外热像仪和压力传感器来记录该锂离子电池爆炸、燃烧的图像、温度和压力.结果表明:电池在过充的过程中,其温度变化分为3个阶段;发生爆炸后,电池的能量主要以燃烧的形式释放,燃烧的火球面积高达770.64 cm2;距电池爆炸15 cm处,最大压强为0.03 MPa,可见电池爆炸会对周围环境造成一定破坏.     

Minimum ignition energy of mixtures of combustible dusts

Most industrial powder processes handle mixtures of various flammable powders. Consequently, hazard evaluation leads to a reduction of the disaster damage that arises from dust explosions. Determining the minimum ignition energy (MIE) of flammable mixtures is critical for identifying possibility of accidental hazard in industry. The aim of this work is to measure the critical ignition energy of different kinds of pure dusts with various particle sizes as well as mixtures thereof.The results show that even the addition of a modest amount of a highly flammable powder to a less combustible powder has a significant impact on the MIE. The MIE varies considerably when the fraction of the highly flammable powder exceeds 20%. For dust mixtures consisting of combustible dusts, the relationship between the ignition energy of the mixture and the minimum ignition energy of the components follows the so-called harmonic model based upon the volume fraction of the pure dusts in the mixture. This correlation provides results which show satisfactory agreement with the experimental values.     

Risk quantification framework of hydride-based hydrogen storage systems for light-duty vehicles

This study aims to develop a quantitative risk assessment (QRA) framework for on-board hydrogen storage systems in light-duty fuel cell vehicles, with focus on hazards from potential vehicular collision affecting hydride-based hydrogen storage vessels. Sodium aluminum hydride (NaAlH₄) has been selected as a representative reversible hydride for hydrogen storage. Functionality of QRA framework is demonstrated by presenting a case study of a postulated vehicle collision (VC) involving the onboard hydrogen storage system. An event tree (ET) model is developed for VC as the accident initiating event. For illustrative purposes, a detailed FT model is developed for hydride dust cloud explosion as part of the accident progress. Phenomenologically-driven ET branch probabilities are estimated based on an experimental program performed for this purpose. Safety-critical basic events (BE) in the FT model are determined using conventional risk importance measures. The Latin Hypercube sampling (LHS) technique has been employed to propagate the aleatory (i.e., stochastic) and epistemic (i.e., phenomenological) uncertainties associated with the probabilistic ET and FT models. Extrapolation of the proposed QRA framework and its core risk-informed insights to other candidate on-board reversible and off-board regenerable hydrogen storage systems could provide better understanding of risk consequences and mitigation options associated with employing this hydrogen-based technology in the transportation sector.