Application of inherent safety principles to dust explosion prevention and mitigation

The aim of the current work is to explicitly link the inherent safety principles of minimization, substitution, moderation and simplification with strategies for dust explosion prevention and mitigation. A brief review of inherent safety and its basic principles is first given. This is followed by a discussion of various ways in which the dust explosion hazard can be minimized, substituted, moderated and simplified. Particular attention is paid to the relationship between each inherent safety principle and (i) various dust explosibility parameters, (ii) alternate methods of processing, (iii) selection of process equipment, and (iv) development and implementation of safe-work procedures. Original research results are presented, along with industrial case studies and previously published results that have been reinterpreted in terms of inherent safety and its basic principles. It is anticipated that this research will be of value to industry as a complement to the relatively well-established suite of engineered and procedural dust explosion risk reduction measures.     

A review on hybrid mixture explosions: Safety parameters,explosion regimes and criteria,flame characteristics

The hybrid mixture of combustible dusts and flammable gases/vapours widely exist in various industries, including mining, petrochemical, metallurgical, textile and pharmaceutical. It may pose a higher explosion risk than gas/vapor or dust/mist explosions since the hybrid explosions can still be initiated even though both the gas and the dust concentration are lower than their lower explosion limit (LEL) values. Understanding the explosion threat of hybrid mixtures not only contributes to the inherent safety and sustainability of industrial process design, but promotes the efficiency of loss prevention and mitigation. To date, however, there is no test standard with reliable explosion criteria available to determine the safety parameters of all types of hybrid mixture explosions, nor the flame propagation and quenching mechanism or theoretical explanation behind these parameters. This review presents a state-of-the-art overview of the comprehensive understanding of hybrid mixture explosions mainly in an experimental study level; thereby, the main limitations and challenges to be faced are explored. The discussed main contents include the experimental measurement for the safety parameters of hybrid mixtures (i.e., explosion sensitivity and severity parameters) via typical test apparatuses, explosion regime and criterion of hybrid mixtures, the detailed flame propagation/quenching characteristics behind the explosion severities/sensitivities of hybrid mixtures. This work aims to summarize the essential basics of experimental studies, and to provide the perspectives based on the current research gaps to understand the explosion hazards of hybrid mixtures in-depth.     

城镇-森林交界域火灾灾害链网络模型构建及风险分析

为确定城镇—森林交界域火灾灾害演化关系及风险特征,预防灾害事件发生,从157个火灾案例中提取43个典型灾害事件,运用灾害链和复杂网络理论,构建城镇-森林交界域火灾灾害链演化模型。使用Python工具对灾害链网络中关键节点、关键边和最短路径分析。结果表明:化工厂爆炸、加油加气站爆炸、城镇火灾、污染水质、污染空气及城市生命线损毁是关键节点,山洪—道路损毁、河流泥沙淤积—山洪、堤坝决堤—山洪、堰塞湖—山洪、森林火灾—城镇火灾是关键边。研究结果可为城镇-森林交界域火灾的防控、断链减灾提供科学依据,具有较高的现实意义。     

An optimal level of dust explosion risk management: Framework and application

The current research provides guidance on the prevention and mitigation of dust explosion using a Quantitative Risk Management Framework (QRMF). Using concepts drawn from previous studies, the framework consists of three main steps: (i) a new combined safety management protocol, (ii) the use of DESC (Dust Explosion Simulation Code) and FTA (Fault Tree Analysis) to assess explosion consequences and likelihood, respectively, and (iii) application of the hierarchy of controls (inherent, engineered and procedural safety). QRMF assessment of an industrial case study showed that the original process was at high risk. DESC simulations and Probit equations determined the destructive percentages. FTAs revealed high probabilities of explosion occurrence; in addition, detailed individual and societal risks calculations were made, before and after the framework was applied. Based on the hierarchy of controls technique, the framework showed significant risk reduction to the point where the residual risk was acceptable for the process.     

Experimental study on the mitigation via an ultra-fine water mist of methane/coal dust mixture explosions in the presence of obstacles

In this paper, experimental investigations were performed for the mitigation via an ultra-fine water mist of methane/coal dust mixture explosions in the presence of obstacles to reveal the effects of the obstacles in this scenario. Two PCB piezo-electronic pressure transducers were used to acquire the pressure history, a Fastcam Ultima APX high-speed video camera was used to visualize both the process of the mixture explosion and its mitigation. The diameters of the coal dust, the types of obstacles and the volumes of ultra-fine water mist were varied in the tests. The parameters of the explosion overpressure and the range of critical volume flux of the ultra-fine water mist for explosion mitigation were determined. The results show that the mixture explosion and its mitigation are primarily influenced by the number, shape and set locations of the obstacles. When the volume flux of the water mist is larger than a certain amount, the mixture explosions and the effects of obstacles can be completely mitigated with the ultra-fine water mist.     

直线管道煤尘爆炸火焰传播规律的试验研究

为提供煤尘爆炸事故预防和缓解所需的科学依据,对煤尘爆炸火焰传播过程进行试验研究。所用试验装置,其主要部分为直径0.3 m的圆形管道与断面边长为80 mm的方形管道对接形成的一个长2 m的爆炸腔体。在其中共进行9次煤尘爆炸试验。结果表明,煤尘爆炸火焰传播具有速度快,波动大,稳定性较差的特点,火焰区长度远大于扬尘区长度,最大火焰速度和传播距离与煤尘量均不存在正比例关系,但存在一个特定的煤尘质量浓度。在这个特定质量浓度处,最大火焰速度达到最大值。当煤尘质量浓度大于这个特定质量浓度时,火焰传播速度曲线整体下降,暂时缺氧被认为是导致这一情况的重要因素。     

Effect of scale on flame speeds of methane-air

Explosions are the main types of accidents causing casualties in underground coal mines. Research on the mechanisms of gas explosions is needed as a basis for the development of techniques and strategies for explosion prevention, suppression, and mitigation. The prevention of loss in explosion accidents and inquiries into their causes require understanding of the explosion process of methane in air. Because of the high cost and safety issues in full scale experiments, the experiments with small scale ducts have become a key alternative approach. Whether the experimental results at small scales agree with those at full scales needs to be investigated to validate the significance of the experimental results at small scale. Numerical simulation was used to obtain the explosion characteristics of a methane-air mixture in a gallery or duct. If the grid size is too fine in the numerical simulation for a methane-air explosion it is difficult to calculate using the present computer resource. If the grid size is too coarse, the considerable error may result. The effect of grid size on results of calculation depends on the scenario being investigated. The effect of grid sizes on simulation accuracy was analyzed in this work. The overpressure and temperature distributions and the flame propagation for the deflagration of methane-air mixtures in a gallery or duct were obtained by the AutoReaGas code at three different scales. The geometry of investigated objects and the grids in the calculation domain were similar in the three cases. The calculated overpressures vary with the scale. The calculated temperatures do not vary with the scale for the three cases.     

煤矿瓦斯爆炸发展规律及防治的综述及展望

针对瓦斯爆炸事故在矿井开采中的危害及防治,从爆炸发展规律和爆炸防治两大方面对国内外瓦斯爆炸研究状况进行了综合评述.国内外学者通过理论法、实验法、数值模拟法对瓦斯爆炸进行研究,瓦斯爆炸发展规律方面的研究涉及到瓦斯爆炸的机理、瓦斯组分及浓度对爆炸发展规律的影响、爆炸发生的条件及危害、爆炸过程中的燃烧阶段变化及流体流动状态变...     

Mitigation performance of the process protection system on the accident consequences of H2S-containing natural gas release and explosion

Toxic loads and explosion overpressure loads pose grave threats to the offshore oil and gas industry. Many safety measures are adopted to prevent and mitigate the adverse impacts caused by toxic loads and explosion overpressure loads. As a general safety barrier, the process protection system has been widely used but rarely evaluated. In order to assess the barrier ability, the mitigation performance of the process protection system is concerned in this study. Firstly, several chain accidents of H₂S-containing natural gas leakage and explosion are simulated by varying the response time of the process protection system with CFD code FLACS. Qualitative assessment is conducted based on the variation of the dangerous load profiles. Furthermore, the quantitative assessment of the mitigation performance is accomplished by considering its ability in reducing the probability of fatality. Emergency evacuation and no emergency evacuation are considered respectively in the quantitative assessment. The results prove that the process protection system takes effect on mitigating the toxic impact and explosion overpressure impact. The results also demonstrate that although the emergency evacuation may result in a severer explosion load to the operator, the process protection system can mitigate the adverse impacts regardless of whether the emergency evacuation is conducted or not.     

Low rate releases of hazardous light gases under semi-confined geometry: A consequence based approach and case-study application

As evidenced by accident statistics, an important factor when considering the safe operation of process plants is the effective mitigation of the effects of gaseous flammable releases, either by a prevention, or a protection approach. A detailed historical analysis was performed considering accidental scenarios associated with the use and management of light gases, starting from raw data selected from FACTS database and analysed by a causal multi-layer method. Results revealed that the major part of the accidental releases involving methane, hydrogen, ethene, ammonia can be attributed to organizational or process/plant immediate causes. As expected, the most frequent scenarios following the release are fire and explosion. We focus our attention on the development of a short-cut method allowing preliminary evaluation of the maximum gaseous build-up under semi-confined conditions, limiting the effects of the fire/explosion scenario to a tolerable level. The limitations of the model that is applied to selected case-studies and require further experimental validation are critically discussed. The results of the application of the model, which can boast of being safe but not disproportionately conservative, can be set as a maximum threshold in proper designing technical measures aiming at limiting the effects to a tolerable level by protection methods, e.g. isolation, venting, suppression and containment.     

Development of a mitigation system against hydrogen-air deflagrations in nuclear power plants

A novel mitigation system against hydrogen-air deflagrations in nuclear power plant buildings is proposed and developed through a series of field experiments using explosion vessels of different volume sizes. The mitigation system is installed on the outer surface of the vessels, and it comprises flame arrester and explosion air bag. The flame arrester is made by stacking 10–20 sheets of fine-mesh wire screens, and the air bag is connected for holding explosion gas. The successful mitigation mechanism is the sequence of pressure-rise reduction by the air bag expansion, flame quenching by the flame arrester, and the slow burning of the gas mixture sucked from the air bag back into the vessel due to the negative pressure caused by the rapid condensation of water vapor inside the vessel. Necessary conditions for the successful mitigation system are discussed, and the practical unit size of flame arrester sheet is recommended.     

矿井瓦斯控爆技术及材料研究进展

瓦斯爆炸灾害防治一直是我国煤矿安全研究的热点、难点。通过对国内外相关文献总结分析,从瓦斯抑爆装置、抑爆介质及抑爆机理3个方面综述了目前国内外矿井瓦斯抑爆技术及抑爆材料的研究现状,提出了未来的发展方向。研究结果表明:瓦斯抑爆技术的有效性和可靠性主要取决于抑爆介质的物理化学性质、控爆空间几何参数、爆炸特性参数和抑爆系统中爆炸探测方式等因素;结合瓦斯爆炸链式反应理论和探测技术的发展,研究应更多地关注抑爆过程的微观特性,揭示其详细的抑爆作用机理,为探寻新型高效、绿色抑爆材料提供更有力的理论支持。     

瓦斯煤尘爆炸特性及传播规律研究进展

概要介绍国内外的瓦斯爆炸和瓦斯煤尘混合物爆炸特性及传播规律研究进展,瓦斯爆炸研究主要集中在瓦斯爆炸压力、火焰、温度等特征参数、不同障碍物对瓦斯爆炸压力、火焰传播的影响以及分岔、拐弯等不同形状管道内的传播规律,而瓦斯煤尘混合物爆炸研究主要集中在瓦斯对煤尘爆炸的最小点火能、爆炸下限、最大爆炸压力等爆炸特性及传播规律的影响。对不同研究人员采用的主要研究指标、手段、方法和研究结论进行综合评述,同时也对爆炸事故人员伤害模型在国内外的研究状况进行讨论,最后指出目前存在的主要问题和下一步的研究方向。     

A quantitative risk management framework for dust and hybrid mixture explosions

Dust and hybrid-mixture explosions continue to occur in industrial processes that handle fine powders and flammable gases. Considerable research is therefore conducted throughout the world with the objective of both preventing the occurrence and mitigating the consequences of such events. In the current work, research has been undertaken to help move the field of dust explosion prevention and mitigation from its current emphasis on hazards (with an accompanying reliance on primarily engineered safety features) to a focus on risk (with an accompanying reliance on hierarchical, risk-based, decision-making tools). Employing the principles of quantitative risk assessment (QRA) of dust and hybrid-mixture explosions, a methodological framework for the management of these risks has been developed.The QRA framework is based on hazard identification via credible accident scenarios for dust explosions, followed by probabilistic fault-tree analysis (using Relex – Reliability Excellence – software) and consequence severity analysis (using DESC – Dust Explosion Simulation Code – software). Identification of risk reduction measures in the framework is accomplished in a hierarchical manner by considering inherent safety measures, passive and active engineered devices, and procedural measures (in that order). An industrial case study is presented to show how inherent safety measures such as dust minimization and dust/process moderation can be helpful in reducing dust and hybrid-mixture explosion consequences in a 400-m³ polyethylene storage silo.     

我国西部中小城镇防震减灾管理体系研究

分析了我国西部中小城镇防震减灾管理现状,借鉴发达国家防震减灾管理的经验,构建了西部中小城镇防震减灾管理体系,包括防震减灾法律保障、行政监管、地震监测预报和预警、防震减灾计划、建筑物和生命线工程的抗震性能保证、防震减灾教育与培训、基层单位对震灾的预防、地震救援组织建设、震灾应急救援服务等彼此关联、相互作用的子系统。指出其建设重点应放在建筑物和生命线工程抗震性能保证、行政监管、防震减灾计划、防震教育培训和基层震灾预防等方面。提出了深化西部中小城镇建设管理体制改革、提高防震减灾社会管理与公共服务水平、加强地震灾害应急救援体系建设等对策和建议。研究成果的运用将有助于增强西部中小城镇的防震减灾管理能力。     

基于氧化还原分析的硫化矿尘爆炸压力预测

为探究可应用于生产现场的硫化矿尘爆炸压力预测方法,基于硫化矿尘爆炸反应机理和粉尘引爆试验数据对硫化矿尘的氧化还原成分与其爆炸压力的相关关系进行分析。研究结果表明：硫化矿尘的还原成分指数与其爆炸压力的相关性极高,尤其是与其爆炸压力峰值的相关性系数高达0.993。整合研究结果形成的硫化矿尘爆炸压力和爆炸压力峰值计算和预测模型,可为金属矿山的硫化矿尘爆炸预防提供决策依据。     

城市控规单元防灾能力评价的有向加权图模型研究

为从城市具体规划建设的视角进行防灾能力评价,找到城市空间与设施的防灾薄弱环节,提升城市的防灾减灾能力,首先,在深入分析城市抗灾-救灾理念的基础上,从抗灾能力和救灾能力2个方面,建立适用于控制性详细规划层面的防灾能力评价指标体系;其次,基于防灾能力评价指标体系构建城市防灾有向加权图模型,通过PageRank算法对用地单元防灾能力值进行排序,实现防灾减灾能力的定量评价;最后,通过某市规划实例检验评价模型,针对控规单元的防灾问题提出规划提升措施。研究结果表明：所构建模型能够实现对各控规单元的防灾能力等级评价,反映城市控规单元防灾能力的分布情况,发现用地单元规划建设中的防灾减灾问题。     

工业生产粉尘爆炸预防和缓解──近期研究与发展综述

本文包括三个方面，即工业粉爆的基础研究、应用研究以及粉尘点人性和可爆性。基础研究包括粉尘云的形成和点火，火焰的传播以及粉煤产生的冲击波。工业预防措施包括惰化和消除点火源。缓解的方法包括隔爆、泄爆、部分惰化、抑爆和全封闭。基础研究和应用研究相互促进。计算机模拟模型可能成为非常有效的方法，也可用于专家系统。