基于MATLAB技术的LPG储罐重大事故动态模拟评价系统开发与应用

为提高人们对LPG储罐重大事故预测、预防水平和抗灾害能力,根据LPG储罐泄漏、扩散、着火、爆炸等事故的发生和发展,建立一套LPG储罐重大事故动态模拟评价方法,在此基础上进行软件系统的功能、模块和数据设计,应用VC与MATLAB可视化面向对象接口技术实现事故后果模拟评价及特征参数随时间、距离变化过程的可视化。该软件能够脱离MATLAB环境运行,实现了评价结果通过图形直观动态显示,可预测特定位置的破坏情况,评价事故影响范围和危害程度。工程应用表明,该评价系统软件用于LPG储罐重大事故的安全评价是可行的,并可用于其他具有着火和爆炸危险性、毒性的重气或液化气体的生产和贮存企业的安全评价。     

液态烃球罐区的危险分析及控制措施

通过危险性分析,对液态烃(LPG)球罐发生火灾爆炸事故后果进行评价。找出容易引起球罐发生火灾爆炸事故的危险因素,如泄漏、雷电、静电、设备故障等。提出防止事故发生的安全措施,降低球罐的危险性。     

粗苯储罐蒸气云爆炸后果定量分析

储罐区防火间距的设计通常依据相关标准规范,本文以山西某化工厂粗苯储罐燃爆事故为例,提出一种更加实用的储罐区防火间距设计方法.粗苯液体沸点低,易挥发,在储罐内液面上方易形成气相空间,遇点火源易引起蒸气云爆炸.基于文献中储罐液位在半罐以上,可保证在任意起爆点位置罐顶均先于罐底发生破裂的结论,建立储罐液位在半罐以上致使罐顶破裂的蒸气云爆炸模型.基于一定的假设,采用TNT当量法,对不同液位状态下5 000m3粗苯储罐发生蒸气云爆炸的后果定量分析,计算蒸气云爆炸的各级损害半径的极值.结果表明:随着储罐内液位的升高,其实际发生蒸气云爆炸的各级损害半径越小,但其理论发生蒸气云爆炸的各级损害半径越大.对于任一液位状态下的储罐蒸气云爆炸情况,其各级损害半径的相对大小为:轻伤区半径R3>财产损失半径R4>重伤区半径R2>死亡区半径R1.     

基于个人风险的土地利用规划在LNG储备库的应用

对基于个人风险的土地利用规划进行研究,确定方法的框架和程序,并应用于某拟建液化天然气储备库周边的土地利用与布局调整。对拟建天然气储备库可能发生的事故,选取蒸气云爆炸及沸腾液体扩展蒸气爆炸进行讨论。在确定事故发生概率及事故后果的基础上,对拟建液化天然气储备库的个人风险进行计算。借鉴英国土地利用规划中个人风险的可接受标准,在液化天然气储备库周围划分三个风险区域,根据各区域的功能规定及储备库周围土地利用现状,对储备库周围的土地利用进行规划与调整。结果表明,液化天然气储备库附近有两处居民区、一个工厂需要搬迁。基于个人风险的土地利用规划方法在合理确定重大工程选址及周边建筑与设施的布局上是行之有效的方法。     

LNG容器蒸气膨胀爆炸特性研究

对液化天然气容器机械破损后的液体过热汽化建立了非平衡相变模型.根据非平衡相变理论,讨论了蒸气膨胀爆炸的过减压极限,并按照气泡半径是否超过临界半径,把气泡的增长分成了束缚和逃逸两个时区,分时区讨论了系统各物理量的变化.通过对液化天然气典型储运工况的计算,得出了不同条件下的过减压极限、压力下降及反弹演化过程,状态参量核化速率的变化过程及最大超压.分析了蒸气膨胀爆炸的基本特性:快速显著核化和沸腾延迟,以及初始条件、损口面积和容器尺度等对物理过程的影响.     

低温容器的蒸汽爆炸现象初探

拟讨论的蒸汽爆炸现象定义为液体因处于较大的过热度而急剧汽化，介质所处空间因大量气体得不到及时释放而使压力骤然升高引发的一种物理爆炸，在低温容器中，液氮，液等介质可能处于数兆帕的压力下，如果容器的某一位置因某种外在原因出现裂口，则其内部的压力会迅速降低，导致液体过热，如果过热度较大，则不能排除低温容器发生蒸汽爆炸的可能性，本文从介绍蒸汽爆炸的机理入手，建立了过热液体中产生均匀核化时汽泡的形成，生长模型，并利用该模型对低温容器的介质发生蒸汽爆炸的可能性进行了探讨。     

基于BP人工神经网络的蒸气云爆炸超压预测的研究

探讨用BP神经网络预测蒸气云爆炸超压的基本原理.重点分析影响蒸气云爆炸超压的各种因素,在此基础上利用BP神经网络算法,通过对80组不同反应活性气体在不同环境条件下爆炸的实验数据进行训练建立了预测蒸气云爆炸超压的网络模型,并对另外20组实验数据进行了爆炸超压预测.预测结果与实测结果基本吻合,说明该模型能够反映蒸气云爆炸超压与其多种影响因素的映射关系,可用于蒸气云爆炸超压预测.该方法为预测蒸气云爆炸超压提供了一条新途径,具有工程实际意义.     

燃气爆炸危险性分析

城市燃气爆炸危危险性分析及评价属安全系统工程的范畴本文针对燃气爆炸的特点给出了燃气爆炸危险性分析的步骤，并对用到的各种方法的理论基础，使用范围和局限性作了简单扼要的介绍。     

燃气爆炸—一个不容忽视的城市灾害

本文论述了燃气爆炸是一个严重的城市灾害，探讨了燃爆的物理力学性质，用模糊数学方法给出了一个评价燃爆危险性软件并针对一个液石油配站做了危险性评价，最后根据燃爆灾害的讨论了简要的对策。     

低温热能朗肯循环发电系统中两相膨胀性能研究（英文）

设计建造了实验装置验证R134a低温热能发电系统中湿蒸汽膨胀性能,在饱和蒸汽做功的研究基础上,在蒸发器与膨胀机之间引入液体管道,通过干饱和蒸汽和饱和液体混合形成湿蒸汽并膨胀做功。实验结果表明,干度为0.9—1.0时两相膨胀可以一定程度上提高发电效率,与理论研究相反;干度更低时发电量低于饱和蒸汽,符合理论分析结果。分析认为,小部分液体参与膨胀过程可以有效提高膨胀机密封程度,降低泄露损失,是发电量呈现小幅上升的关键原因。本研究为低温热能发的系统的设计提供了理论和实验依据。     

Metallurgical failure analysis of a propane tank boiling liquid expanding vapor explosion (BLEVE)

A severe fire and explosion occurred at a propane storage yard in Truth or Consequences, N.M., when a truck ran into the pumping and plumbing system beneath a large propane tank. The storage tank emptied when the liquid-phase excess flow valve tore out of the tank. The ensuing fire engulfed several propane delivery trucks, causing one of them to explode. A series of elevated-temperature stress-rupture tears developed along the top of a 9800 L (2600 gal) truck-mounted tank as it was heated by the fire. Unstable fracture then occurred suddenly along the length of the tank and around both end caps, along the girth welds connecting the end caps to the center portion of the tank. The remaining contents of the tank were suddenly released, aerosolized, and combusted, creating a powerful boiling liquid expanding vapor explosion (BLEVE). Based on metallography of the tank pieces, the approximate tank temperature at the onset of the BLEVE was determined. Metallurgical analysis of the ruptured tank also permitted several hypotheses regarding BLEVE mechanisms to be evaluated. Suggestions are made for additional work that could provide improved predictive capabilities regarding BLEVEs and for methods to decrease the susceptibility of propane tanks to BLEVEs.     

Risks of Fire and Explosion Associated With the Increasing Use of Liquefied Petroleum Gas

Liquefied petroleum gas (LPG) has been in use as household fuel all over the world for several decades. Until the late 1980s, its use in the developing world was largely confined to the economically well-off strata of the society but it has since spread over a much larger catchment. The increasing use of LPG has enhanced and generalized the risk of a “boiling liquid expanding vapor explosion” (BLEVE). This is evidenced from the reports which appear now and then of a LPG cylinder having exploded in a household, some workshop, or on a bus or a train. In fact some very major tragedies have been triggered by such explosions which also set off fires and cause secondary accidents. This paper describes what BLEVEs are and how can they be controlled. The paper focuses on hazards of BLEVE in large installations which deal with LPG, and other pressure-liquefied gases and discusses the nature, mechanism, and means of control of BLEVEs.     

Uncertainty quantification in the health consequences of the boiling liquid expanding vapour explosion phenomenon.

A methodology for estimating the risk owing to the phenomenon of boiling liquid expanding vapour explosion (BLEVE) in the presence of uncertainties both in the model and in the parameters of the models is presented. BLEVE takes place when a tank containing liquefied petroleum gas (LPG) is exposed to fire and fails catastrophically. Two models have been used in the estimation of the intensity of thermal radiation from the resulting fireball, namely the solid-flame model assuming an emission power independent of the combustion mass and the point-source model that estimates the emissive power as a function of the combustion mass. Three measures of the BLEVE consequences, the intensity of thermal radiation, the dose of thermal radiation and the probability of loss of life as a result of the exposure to the thermal radiation and as a function of the distance from the center of the tank have been considered. Uncertainties in the exact values of the parameters of the models have been quantified and the resulting uncertainties in the three consequence measures have been assessed. A sensitivity analysis on the relative contribution of the uncertainty in each of the input variables to the uncertainties of the consequence measures has been performed. One conclusion is that the uncertainties in the probability of loss of life are mainly due to the uncertainties in the model of the physical phenomenon rather than to the uncertainties of the dose-response model.     

A simplified model to predict the thermal response of PLG and its influence on BLEVE

A simplified model has been developed to describe the thermal response of pressure liquefied gas (PLG) tanks subjected to fire. The development of the stratification layer is considered in this model. Comparison of results with available experimental data shows that our proposed model can reasonably predict the thermal response. The effect of stratification on the liquid energy is also summarized. Results show that the pressure in the tank rises faster as a result of thermal stratification, and for the same tank pressure the energy in the liquid is less when the liquid is stratified. Stratification can reduce the severity of hazards of boiling liquid expanding vapor explosion (BLEVE).     

Consequence analysis in LPG installation using an integrated computer package

This paper presents the prototype of the computer code, Atlantide, developed to assess the consequences associated with accidental events that can occur in a LPG storage plant. The characteristic of Atlantide is to be simple enough but at the same time adequate to cope with consequence analysis as required by Italian legislation in fulfilling the Seveso Directive. The application of Atlantide is appropriate for LPG storage/transferring installations. The models and correlations implemented in the code are relevant to flashing liquid releases, heavy gas dispersion and other typical phenomena such as BLEVE/Fireball. The computer code allows, on the basis of the operating/design characteristics, the study of the relevant accidental events from the evaluation of the release rate (liquid, gaseous and two-phase) in the unit involved, to the analysis of the subsequent evaporation and dispersion, up to the assessment of the final phenomena of fire and explosion. This is done taking as reference simplified Event Trees which describe the evolution of accidental scenarios, taking into account the most likely meteorological conditions, the different release situations and other features typical of a LPG installation. The limited input data required and the automatic linking between the single models, that are activated in a defined sequence, depending on the accidental event selected, minimize both the time required for the risk analysis and the possibility of errors. Models and equations implemented in Atlantide have been selected from public literature or in-house developed software and tailored with the aim to be easy to use and fast to run but, nevertheless, able to provide realistic simulation of the accidental event as well as reliable results, in terms of physical effects and hazardous areas. The results have been compared with those of other internationally recognized codes and with the criteria adopted by Italian authorities to verify the Safety Reports for LPG installations. A brief of the theoretical basis of each model implemented in Atlantide and an example of application are included in the paper.     

Assessment of an explosive LPG release accident: a case study

In the present paper, an accident occurred during a liquefied petroleum gas (LPG) tank filling activity has been taken into consideration. During the transfer of LPG from the source road tank car to the receiving fixed storage vessel, an accidental release of LPG gave rise to different final consequences ranging from a pool fire, to a fireball and to the catastrophic rupture of the tank with successive explosion of its contents. The sequence of events has been investigated by using some of the consequence calculation models most commonly adopted in risk analysis and accident investigation. On one hand, this allows to better understand the link between the various events of the accident. On the other hand, a comparison between the results of the calculations and the damages actually observed after the accident, allows to check the accuracy of the prediction models and to critically assess their validity. In particular, it was shown that the largest uncertainty is associated with the calculation of the energy involved in the physical expansion of the fluid (both liquid and vapor) after the catastrophic rupture of the tank.     

Risk-informed selection of a highway trajectory in the neighborhood of an oil-refinery.

A methodology for characterizing alternative trajectories of a new highway in the neighborhood of an oil-refinery with respect to the risk to public health is presented. The approach is based on a quantitative assessment of the risk that the storage facilities of flammable materials of the refinery pose to the users of the highway. Physical phenomena with a potential for detrimental consequences to public health such as BLEVE (Boiling Liquid Expanding Vapor Explosion), Unconfined Vapor Cloud Explosion, flash fire and pool fire are considered. Methodological and procedural steps for assessing the individual risk around the tank farm of the oil-refinery are presented. Based on the individual risk, group risk for each alternative highway trajectory is determined.     

A study of the behaviour of a protected vessel containing LPG during pool fire engulfment

Theoretical and experimental investigations of various methods for protection against fires of vessels containing liquefied petroleum gases (LPG) (safety relief valves, intumescent fire retardant coatings, thermal isolation) have been carried out. A simple mathematical model has been proposed, which describes dependences of various parameters on time. These parameters are temperature, pressure and mass of LPG, temperatures of the vessel's walls and thermal protection layer. The case of total fire engulfment of the vessel with LPG was considered. Experiments have been executed, which were aimed on the investigation of the behaviour of vessels with LPG (50 l), equipped with protective devices during total fire engulfment. It was found out that the safety valve prevented an explosion of the vessels without any other protective measures. The presence of the intumescent fire retardant coating caused a significant delay in operation of the safety valve. A rather good agreement between the theoretical and experimental data was obtained. It has been revealed that the considered methods for protection of LPG vessels are promising in regard to prevention of explosions in these vessels at the fire engulfment.     

Experimental and analytical investigation of thermal coating effectiveness for 3m(3) LPG tanks engulfed by fire

Two large-scale diesel pool fire engulfment tests were carried out on LPG tanks protected with intumescing materials to test the effectiveness of thermal coatings in the prevention of hot BLEVE accidental scenarios in the road and rail transport of LPG. A specific test protocol was defined to enhance reproducibility of experimental tests. The geometrical characteristics of the test tanks were selected in order to obtain shell stresses similar to those present in full-size road tankers complying to ADR standards. In order to better understand the stress distribution on the vessel and to identify underlying complicating phenomena, a finite element model was also developed to better analyze the experimental data. A non-homogeneous and time-dependent effectiveness of the fire protection given by the intumescing coating was evidenced both by finite element simulations and by the analysis of the coating after the tests. The results of the fire tests pointed out that the coating assured an effective protection of the tanks, consistently increasing the expected time to failure. The data obtained suggest that the introduction of fire protection coatings may be a viable route to improve the safety of the LPG distribution chain.