危险化学品事故后果计算过程探讨

基于事故后果的风险评估方法是国内外进行安全评价和土地使用安全规划的基础方法之一。本文基于危险化学品种类和危险装置类型，对可能发生的事故情景和相应事故后果计算模型的选择方法进行了阐述，针对易燃、易爆、有毒危险化学品的事故后果计算过程进行了系统分析。最后对本文提出的事故后果分析方法进行了实例应用。本文的研究成果可为安全评价或土地使用安全规划等工作的开展提供必要的参考。     

安全评价方法在危险废物处置环境风险评价中的应用探讨

对安全评价方法在危险废物处置建设项目环境风险评价中的运用进行初步探索。主要用"工艺过程风险因素分析表"对工艺过程潜在风险性识别;用蒙德法进行源项分析;用池火灾模型、蒸气云爆炸伤害模型对易燃、易爆物质的火灾、爆炸等重大事故后果进行计算,得出人员的伤亡半径和财产损失半径等参数,以便于判断风险的可接受水平。分析结果表明:采用安全评价方法对危险废物处置建设项目进行环境风险评价是适用的、可行的。     

扑救液化石油气储罐爆炸火灾安全距离的确定

液化石油气储罐爆炸火灾是一类比较难于扑救的特殊火灾，如何根据现场的情况快速评估事故危害，并确定灭火指挥和人员疏散的安全距离，是消防指挥员指挥决策的重要问题，也是难点问题。本文研究了液化石油气储罐发生BLEVE时的热辐射和冲击波计算方法，并导出了安全距离的确定方法。对于消防指挥员快速决策具有十分重要的意义。     

危险工业设施周边土地利用规划研究

由于工业设施的存在,其周边区域常常受到潜在工业事故的威胁,为了减小这种风险,必须对这些区域进行合理的土地利用规划。借鉴欧洲研究者的研究方法,利用基于后果的风险评价方法确定不同破坏分区的边界,并将不同土地利用类型的脆弱等级引入土地利用规划,结合二者的结果,依据决策矩阵得到规划决策意见。通过将上述方法应用在某拟建的LPG中转站周边区域,以丙烷泄漏引起的沸腾液体蒸气爆炸为例,将风险分析和决策结果显示在地理信息系统上。案例分析表明该设施对周边区域影响较大,需要对其进行重新选址。     

有毒有害蒸气云扩散的危害估算

因事故排放形成的有毒有害蒸气云,有可能造成爆炸、火灾、中毒等危害后果,但危害后果的大小(危害程度),则与事故造成危害的时刻(延迟时间)有关。笔者在以往研究成果基础上,考虑该因素,并通过引入正态分布假设,时、空变换及误差分析,给出了估算危害程度(特别是延迟爆炸危害)的有效而简便方法,补充了以往危害估算方法(不考虑延迟时间)的不足,提高了危害后果估算精度,可广泛应用于生产安全评价、环境风险评价、风险工程设计、事故应急预案、事故应急救援等工作领域,对于保障环境安全具有显著的科学价值与现实意义。     

Expansion-controlled evaporation: a safe approach to BLEVE blast

A new method is presented to calculate the blast effects originating from an exploding vessel of liquefied gas. Adequate blast calculation requires full knowledge of the blast source characteristics, i.e., the release and consequent evaporation rate of the flashing liquid. As the conditions that allow explosive evaporation are not entirely clear and the evaporation rate of a flashing liquid is unknown, safe assumptions are the starting point in the modelling. The blast effects from a BLEVE are numerically computed by imposing the vapour pressure of a flashing liquid as boundary condition for the gas dynamics of expansion. The numerical modelling is quantitatively explored just for liquefied propane. In addition, it is demonstrated that often an estimate of BLEVE blast effects is possible with very simple acoustic volume source expressions.

The modelling shows that the rupture of a pressure vessel containing a liquefied gas in free space only develops a blast of significant strength if the vessel nearly instantaneously disintegrates. Even if a rupture and the consequent release and evaporation of a liquefied gas extend over just a short period of time, the blast effects are minor.     

Assessing the hazards from a BLEVE and minimizing its impacts using the inherent safety concept

Many worlds' major process industry accidents are due to BLEVE such as at Feyzin, France, 1966 and San Juan Ixhuatepec, Mexico City, 1984. One of the approaches to eliminate or minimize such accidents is by the implementation of inherently safer design concept. This concept is best implemented where the consequence of BLEVE can be evaluated at the preliminary design stage, and necessary design improvements can be done as early as possible. Thus, the accident could be avoided or minimized to as low as reasonably practicable (ALARP) without resorting to a costly protective system. However, the inherent safety concept is not easy to implement at the preliminary design stage due to lack of systematic technique for practical application. To overcome these hurdles, this paper presents a new approach to assess process plant for the potential BLEVE at the preliminary design stage and to allow modifications using inherent safety principles in order to avoid or minimize major accidents. A model known as Inherent Fire Consequence Estimation Tool (IFCET) is developed in MS Excel spreadsheet to evaluate BLEVE impacts based on overpressure, radiation heat flux and missile effects. In this study, BLEVE impacts are the criteria used as the decision-making for the acceptability of the design. IFCET is integrated with iCON process design simulator for ease of data transfer and quick assessment of potential BLEVE during the design simulation stage. A case study was conducted to assess of potential BLEVE from a propane storage vessel at the design simulation stage using this new approach. The finding shows promising results that this approach has a potential to be developed as a practical tool.     

液化石油气储罐爆炸碎片抛射的蒙特卡罗分析

液化石油气发生BLEVE具有极大的危害性,如何对危害性进行定量分析和评估是风险分析评价的重要内容。由于BLEVE的发生具有很大的不确定性,其造成的危害也存在不确定性,这给定量分析评价带来了较大的困难。该文从风险工程学的角度对BLEVE引起的碎片抛射可能对人员造成的危害风险进行了定量分析,对不确定性参数利用有关的资料和数据确定其概率密度分布,并利用蒙特卡罗方法进行模拟,从而计算了碎片抛射范围。对于定量评价BLEVE风险具有重要意义。     

城市土地使用安全规划的方法与内容探讨

本文分析了几起与土地使用安全规划相关的重大事故案例,简要介绍了国内外土地使用安全规划的法律、法规要求,论述了安全规划的方法和风险标准,提出了我国城市土地使用安全规划的主要内容和程序,研究分析了安全专项规划和城市功能区安全治理规划的基本要求.     

Risk assessment in support to land-use planning in Europe: Towards more consistent decisions?

Recognising the importance of establishing appropriate separation distances between hazardous installations and vulnerable residential areas for mitigating the effects of industrial accidents, the European legislation for the control of major accident hazards - the so-called Seveso II Directive - calls for procedures ensuring that technical advice is taken systematically into account for land-use planning (LUP) purposes. Due to historical, administrative, cultural and other reasons, these European Union’s Member States which have consolidated procedures for addressing this issue, have employed different approaches, methods and criteria, with a potential for great divergence in the resulting land-use planning decisions. In order to address this situation and to increase consistency and ‘defendability’ of land-use planning decisions in the EU, a European Working Group has been established and is operating under the coordination of the European Commission’s Joint Research Centre (JRC). This Group, consisting of experts from the EU Member States, the industry and the academia, is trying to understand the different approaches and their implications to LUP decision-making, to develop guidelines in support to these decisions and to examine data sources and tools for consistent application of risk assessment in support to LUP. This paper presents the activities of the Group, reviews the situation with respect to LUP in Europe and discusses whether a direction towards more consistent LUP decisions is being followed in Europe.     

Design for safety in Safecharts with risk ordering of states

Safecharts is a variant of Statecharts intended exclusively for safety critical systems design. With two separate representations for functional and safety requirements, Safecharts brings the distinctions and dependencies between them into sharper focus, helping both designers and auditors alike in modelling and reviewing safety features. Safecharts incorporates ways to represent equipment failures and failure handling mechanisms and uses a safety-oriented classification of transitions and a safety-oriented scheme for resolving any unpredictable non-deterministic pattern of behaviour. It achieves these through an explicit representation of risks posed by hazardous states by means of an ordering of states and a concept called risk band. Recognising the possibility of gaps and inaccuracies in safety analysis, Safecharts do not permit transitions between states with unknown relative risk levels. However, in order to limit the number of transitions excluded in this manner, Safecharts provides a default interpretation for relative risk levels between states not covered by the risk ordering relation, requiring the designer to clarify the risk levels in the event of a disagreement and thus improving the risk assessment process.     

An innovative and comprehensive approach for the consequence analysis of liquid hydrogen vessel explosions

Hydrogen is one of the most suitable solutions to replace hydrocarbons in the future. Hydrogen consumption is expected to grow in the next years. Hydrogen liquefaction is one of the processes that allows for increase of hydrogen density and it is suggested when a large amount of substance must be stored or transported. Despite being a clean fuel, its chemical and physical properties often arise concerns about the safety of the hydrogen technologies. A potentially critical scenario for the liquid hydrogen (LH₂) tanks is the catastrophic rupture causing a consequent boiling liquid expanding vapour explosion (BLEVE), with consequent overpressure, fragments projection and eventually a fireball. In this work, all the BLEVE consequence typologies are evaluated through theoretical and analytical models. These models are validated with the experimental results provided by the BMW care manufacturer safety tests conducted during the 1990's. After the validation, the most suitable methods are selected to perform a blind prediction study of the forthcoming LH₂ BLEVE experiments of the Safe Hydrogen fuel handling and Use for Efficient Implementation (SH₂IFT) project. The models drawbacks together with the uncertainties and the knowledge gap in LH₂ physical explosions are highlighted. Finally, future works on the modelling activity of the LH₂ BLEVE are suggested.     

A closer look at BLEVE overpressure

The overpressure produced by the boiling liquid expanding vapor explosion (BLEVE) is still not well understood. Various methods have been published on the overpressure modeling in the far field. They mostly differ by the modeling of the expansion energy, used to scale the distance to the source where the overpressure needs to be calculated. But these methods usually include a experimentally fitted reduction factor, and are mostly overestimating the overpressures. Today there is a growing interest in modeling the BLEVE overpressure in the near field, for studying the blast effect on critical infrastructure such as bridges and buildings. This requires a much better understanding of the BLEVE blast. This paper goes deeper in the understanding of the physical phenomenon leading to the BLEVE blast wave generation and propagation. First, mid-scale BLEVE experiments in addition to new experimental data for near field blast from a small scale supercritical BLEVE are analyzed. And second, an analysis method of the shocks observed in the experiments is presented based on fundamental gas dynamics, and allows the elaboration of a new modeling approach for BLEVE overpressure, based on the calculation of the initial overpressure and radius of the blast.     

Case study: Assessment on large scale LPG BLEVEs in the 2011 Tohoku earthquakes

After the 2011 Tohoku earthquakes, several chemical and oil complexes on the Pacific Ocean shoreline of northeast Japan experienced massive losses. In Chiba, a refinery operated by Cosmo Oil lost 17 LPG storage vessels which were either heavily damaged or totally destroyed by fires and explosions in the refinery. These large vessels ranged in size from 1000 to 5000 m³. The estimated volume of LPG at the time of the incident was between 400 and 5000 m³ for each vessel. Five boiling liquid expanding vapor explosions (BLEVEs) of LPG occurred, resulting in huge fire balls measuring about 500 m in diameter.A BLEVE is defined as the explosive release of expanding vapor and boiling liquid when a container holding a pressure-liquefied gas fails catastrophically. It is thus important to estimate the physical properties of superheated liquids: the thermodynamic and transport properties, the intrinsic limits to superheating and depressurization, and the nature of thermodynamic paths. Also it is hoped to provide better understanding of the vessels designed, manufactured, installed, and operated to reduce or eliminate the probability that a sequence of events will result in BLEVE or loss of primary containment. Knowledge of these matters is still incomplete. The objective of this research is to estimate the significant BLEVE phenomenon in very large scale spherical vessels based on published information in Japan. There are some models predicting BLEVEs. However, it is essential to know if this is true for very large scales such as spheres since validation is usually rare to provide confidence in estimating the superheated liquids behaviors. To this end, comparing with the information on this event, the conditions in the five LPG vessels at the time of the BLEVE were determined in terms of: duration of vessel failure (time to BLEVE); mass fraction in the vessel with time; temperature distribution in the liquid and vapor region and pressure within the vessel (e.g. initial pressure and internal high-speed transient pressure during failure), by means of a computer program AFFTAC Analysis of Fire Effects on Tank Cars, which solves heat conduction, stress and a failure model of the tank, a thermodynamic model of its fluid contents, and a flow model for the lading flowing through the safety relief device. Subsequently, the consequences from the sphere BLEVE, such as the expected fireball diameter and duration and the expected blast overpressure produced by the BLEVE failures, are also subjects of active research. Here the blast using the methods of PHAST and SFPE Handbook of Fire Protection Engineering was calculated.Results suggest that methodologies here used gave reasonable estimations for such real and huge BLEVEs in a validated way, which may provide valuable guidance for risk mitigation strategy with regard to LPG facility in design, emergency planning, resiliency, operations, and risk management.     

风险矩阵法在危险有害因素分级中的应用

为减少风险分级时产生的风险结,采用Borda序值法改进原有的风险矩阵法。改进后的风险矩阵法通过计算Borda数,依据Borda数的大小对风险进行排序,使得风险等级数量大量增加,从而减少风险矩阵中风险结的数量。将该方法应用于某烧碱装置危险有害因素分级管理,对生产过程中的9种主要危险有害因素进行排序,得出它们可以分为6级,而应用原始的风险矩阵法得到的分级数为3级。然后,依据分级结果提出针对性的安全对策措施。     

火球热辐射后果计算动态模型的应用

为了精确地评估火球的热辐射后果,需要深入研究火球热负荷对影响区域暴露人员所造成的伤害.详细介绍了具有时间属性的火球热辐射动态模型,以实例描绘了火球直径、高度以及目标接受到的热通量等火球参数的动态变化规律.结果表明:具有时间属性的火球热辐射动态模型计算出的热辐射值小于静态模型计算的值,动态模型有可能更准确地描述火球参数的实际动态变化,进而合理地确定火球热辐射的人员伤亡区域,并为过热可燃液体容器的安全设计及风险分析提供一种新的后果评估技术及方法.     

Decision-making on process risk of Arctic route for LNG carrier via dynamic Bayesian network modeling

An increasing number of ships have chosen the suitable route to transport in Arctic waters during summer. Seeking a suitable model for risk decision-making in route planning is a necessary research topic at present. Due to its complex natural environment, there is significant uncertainty regarding ship navigation safety in Arctic waters. The process risk-based decision-making method to support route planning is established based on the dynamic Bayesian network (DBN) risk assessment model for LNG carrier collision with ice or obstacles in Arctic waters. The decision-making process for ship navigation is dynamically associated with time. Therefore, a Markov Chain (MC) is built for each dynamic node in Bayesian belief network (BBN) to realize DBN associated risk assessment, which is called process risk and is applied to decision-making. Three possible routes for ships sailing from the Vikitsky Strait to the Long Strait in Arctic waters were selected in conjunction with the objective daily change data of wind speed, temperature, wave height, and ice condition. Simulations for risk decision-making in the ship navigation process are performed. Application examples show that the ship selected either ROUTE2 (Vikitsky Strait – Laptev Sea – Sannikov Strait – Eastern Siberian Sea – Long Strait) or ROUTE3 (Vikitsky Strait – Laptev Sea – Proliv Dmitriya Lapteva – Eastern Siberian Sea – Long Strait) in August as the best navigable route.     

重大危险源区域事故应急非结构化模糊决策应用研究

针对目前我国应对重大危险源突发事故的管理和决策主要依赖于相关领导或专家掌握的知识及经验的现状,将非结构化模糊决策方法(Non-structural Fuzzy Decision Method,NSFDM)和事故后果模拟方法相结合,以区域范围内受重大危险源潜在事故影响的企业为决策对象,以减小事故影响范围,降低事故严重程度为目标,建立起重大危险源区域事故应急决策的多准则决策方法,以期帮助安监职能部门优化配置应急救援资源,提高应急响应绩效,减少国家和人民的经济和财产损失。以广州市某公司丙烷储罐区为实例,在对其进行沸腾液体扩展蒸气爆炸(Boiling Liquid Expanding Va-por Explosion,BLEVE)事故模拟的基础上,运用非结构化模糊决策方法,对该丙烷储罐区BLEVE事故的处理,提供了应急决策支持。     

基于风险的危险品道路运输安全容量研究

为了确定危险品道路运输安全容量，保障危险品道路运输安全，基于风险理念，使用对比研究方法，提出危险品道路运输个人风险基准，建立改进的危险品道路运输定量风险评估模型。结合提出的风险基准，提出危险品运输安全容量确定方法，解决了单一类别和多种类别危险品运输安全容量确定问题。研究结果表明:在某城市化工集聚区的实例应用该方法，能够大幅度降低危险品道路运输潜在生命损失，有助于保障危险品道路运输安全。     

钻探工程施工中危险源辨识、风险评价及其控制

对钻探工程施工中存在的危险、危害因素进行了辨识和分析,采用预先危险性分析方法及安全因素影响风险评价方法对施工过程中危险源的危险等级和安全因素影响等进行了分析和评价,针对重大危险源采用了安全技术和安全管理控制措施。首先对能量危害物质、失控(包括生产、控制、安全装置和辅助设施等故障及人员失误)、管理缺陷及客观因素进行危险源辨识;第二,评价危险源危害因素主次;第三,采用安全技术和安全管理措施有效地对车辆伤害、登高作业、防雷安全、用电安全、机械安全及预防自然灾害(火灾)等重大危险源进行控制。通过实践表明,福建省121地质大队采用该方法对钻探工程项目的危险源进行了有效地控制,实现了钻探安全生产。