液氨储罐事故性泄漏扩散过程模拟分析

液氨是化工企业常用的原料，而每年因为液氨储罐的泄漏造成的事故也十分频繁，液氨属于高度危险性物质，一旦泄漏极可能造成灾难性后果。本文探讨了描述液氨储罐事故性泄漏及扩散过程的数学模型，并用所建模型针对某市化学园区某化工公司液氨储罐工程建设项目进行模拟分析。从模拟结果来看，采用数学模型的方法对事故后果进行预测和分析具有一定程度的可靠性，对于救灾、重大危险源编制应急事故预案以及对新建项目进行危险性预评价都具有一定程度的指导意义。     

液氨储罐危险因素辨识

液氨储罐在工业中应用广泛,液氨储罐属于介质为毒性且易燃易爆的压力容器,在实际生产中发生过多起爆炸、中毒、泄漏、火灾事故,本文分析了液氨储罐可能存在的危险因素,对液氨储罐物理爆炸能量和爆炸冲击波伤害范围进行了估算,提出了预防爆炸、中毒、泄漏、火灾事故发生的安全控制措施及建议.     

基于质量流率离散方法的液氨储罐泄漏扩散模型的研究

针对高斯模型中忽略物质质量流率的变化导致模拟结果与实际存在偏差的问题,将物质质量流率根据泄漏持续时间进行离散化处理,获得不同时间段的物质泄漏量,以此对高斯烟团叠加模型进行修正,得到若干烟团不同时刻的浓度分布模型,并以液氨储罐泄漏事故为研究对象,获得较恒速泄漏条件具有明显差异的有毒云团危害区域。针对其后果偏差产生的原因——罐内初始压力Pn及储罐的充装水平α进行研究,分别比较在不同的Pn及α取值情况下泄漏后果的变化及差异。研究表明,增大Pn或减小α能够有效减小液氨泄漏的危害距离,并且会减小恒速泄漏条件分析后果的偏差,对液氨等罐区的管理提供依据。     

电厂脱硝工程液氨储罐泄漏环境风险分析

以某发电厂液氨储罐为例,从风险识别、源项分析、后果计算和事故风险防范措施等方面对储罐进行环境风险分析,并进行了模拟计算.结果表明,项目的最大可信事故为液氨储罐泄漏事故,液氮储罐的泄漏概率为7.96×10-6a-1,液相的泄漏速率为45.7 kg/s,气相的泄漏速率为3.74 kg/s,两相的泄漏速率为7.85 kg/s,闪蒸的蒸发速率为9.96 kg/s,并确定了氨气扩散的危害范围和相应防治措施.     

某液氨储罐泄漏的后果分析及对策

对某液氨储罐泄漏进行了后果分析,模拟计算出氨对人的毒性影响范围,爆炸下限的影响距离,形成闪火的距离,发生燃烧的热辐射对人员和设备的危害程度以及发生爆炸超压对人员和建筑物的危害程度。提出了安全对策措施。     

ALOHA在突发性大气污染事故中的应用

以天津市某化工厂液氨罐泄漏为背景,在氨泄漏后果分析的基础上,用ALOHA(有害大气区域定位)模拟软件对事故影响范围进行模拟,得到可能事故场景下的氨气扩散区域、闪火可燃区域和蒸气云爆炸超压影响区域,以及射火和BLEVE火球热辐射影响.结果表明,液氨爆炸和火灾事故中BLEVE事故造成的危害范围最大,其次是蒸气云、闪火,最后是射火.液氨泄漏扩散事故影响范围可达几千米,应针对不同伤害区域采取不同方式和不同程度的救援措施.     

液氨泄漏事故伤害范围模拟及人员疏散研究

基于高斯烟羽模型,应用风险评估软件对液氨储罐在不同泄漏模式下的液氨伤害范围进行模拟,得出各模式下液氨伤害范围的变化规律,并分析了风速对液氨扩散的影响作用。制定了液氨储罐特定泄漏模拟场景下的人员疏散路径,为液氨泄漏事故下的人员应急救援以及疏散等提供参考。     

大型LNG储罐防火间距分析

国内LNG接收站产业发展日益壮大,LNG储罐的规模也随之呈现大型化的趋势,其带来对周边储罐的安全问题成为关注的焦点.针对大型LNG储罐防火间距的分析,依据国际广泛接受的美国NFPA 59A-2009和欧洲EN1473-2007标准,分别采用事故后果模拟手段和危险性评估方法确定储罐防火间距,事故场景分别考虑了罐顶池火灾和卸料管线发生直径50mm孔洞泄漏火灾.在此基础之上,对事故后果模拟得到的结果进行分析,明确储罐防火间距,从而为企业对LNG储罐区进行布局设计提供参考指导.     

基于蒙特卡罗法的圆柱形储罐泄漏时间分析

泄漏持续时间是影响事故后果定量风险评价的关键因素之一.已有的泄漏时间计算多是基于参数确定性考虑,计算结果往往与实际数值有较大的偏差.在分析泄漏源模型的基础上,推导了圆柱形储罐泄漏时间理论计算公式,并从影响因素的不确定性分析出发,选用已知状态变量下的分布函数加以描述.同时,结合蒙特卡罗法解决了输入参数的不确定性.通过实例模拟,揭示了连续泄漏事故场景下储罐内物料发生完全泄漏的时间分布规律,并提出了最大有效泄漏持续时间概念.     

化工园区泄漏事故安全风险评估模式研究

为减少化工事故频发造成严重人员伤亡及财产损失,在分析危化品泄漏事故类型的基础上,从事故发生概率和事故后果两方面提出危化品泄漏事故风险评估模型.以中毒事故为例,对重庆长寿化工园区内某企业一液氨储罐进行风险评估.基于概率模型计算中毒事故概率,结果表明该储罐发生泄漏引起中毒的概率较小;数值模拟结果显示:影响范围随时间的增加而...     

Class-2 hazmat transportation consequence assessment on surrounding population

The transportation of hazardous materials by road is an utmost necessity of the world for the societal benefits, but at the same time the activity is inherently dangerous. Incidents involving hazardous material (hazmat) cargo particularly the class-2 materials can lead to severe consequences in terms of fatalities, injuries, evacuation, property damage and environmental degradation. The rationale behind considering class-2 hazmats is that they pose the greatest danger to the people and property along the transport route because of their storage condition on the transport vessel. They are stored either in pressurized vessels or in cryogenic containers. Any external impact due to collision may cause catastrophic failure of transport vessels, known as BLEVE (Boiling Liquid Expanding Vapour Explosion) with devastating consequences. Further, any continuous release from containment may cause what is known as ‘Unconfined Vapour Cloud Explosion’ (UVCE). Historically frequency of BLEVE occurrence is of the order of 1 × 10⁻⁶ per year or less, but other release scenarios e.g. a large vapour or liquid leaks are more probable and could also have devastating effects on the surrounding population. As such, the paper discussed various event scenarios and the consequences taking examples of a class-2.1 material (1,3 butadiene) and another class-2.3 (ammonia) hazmat. Comparative analysis suggests that per ton basis a rupture of ammonia tanker gives rise to larger impact areas and poses larger lethality risks compared to 1,3 butadiene as far as toxic effects are concerned. Besides, from fireball fatality on similar basis propylene causes higher consequence distance than LPG followed by ethylene oxide and 1,3 butadiene. The impact zone study results may be utilized as inputs for identifying the potential vulnerable area on a GIS enabled map, along a designated State highway route passing through an important industrial corridor in western India.     

Influence of wind speed profile and roughness parameters on the downwind extension of vulnerable zones during dispersion of toxic dense gases

The accidental release of toxic chemicals, which are heavier than air and stored under pressure, may create an emergency scenario in an industrial plant. The extension of vulnerable distance in the downwind direction is an important criterion in framing an emergency management plan of that industrial area. There are several studies showing the role of surface level meteorological and topographical features on its propagation and dispersion just after its release from a container. In the present study, vertical variation of wind speed in the atmospheric boundary layer and surface roughness parameter have been considered to study their roles on the impact of downwind extension of vulnerable distances. A catastrophic release from a tonner having 900 kg of liquid chlorine has been considered, and SAFETI Micro developed by DNV Technica, UK has been utilized in the consequence analysis of this release. The analysis results have been explained for various atmospheric stability classes and surface wind speeds.     

Analyzing effective factors on leakage-induced hydrogen fires

Currently, novel energy resources are receiving increasing attention as a response to the limitation in fossil fuels as well as their adverse effects on human health. Hydrogen, one of the most abundant elements on the earth, can be regarded as a new energy source to replace fossil fuels. Therefore, safety assessment of the relating processes is very crucial by increasing use of hydrogen as a fuel source. In this regard, consequence analysis for risk assessment and power reduction is very important. The present study aims at modeling hydrogen dispersion along with consequence analyses for such events as jet fire and flash fire. The model was validated by using the data derived from a study on hydrogen leakage in supply pipelines in the laboratory of the University of Pisa. Modeling results reveal that ambient conditions will impose a milder impact on leakage consequences if internal pressure is high in release source. The safe distance was also estimated to be 14 m. Dispersion consequence modeling was performed, followed by the evaluation of the effect of environmental (i.e., stability, ambient temperature, surface roughness, wind speed, and humidity) and process (i.e., vessel temperature and pressure, leakage diameter, and releasing point height) parameters on maximum size flammable vapor cloud and maximum level jet fire radiation on the ground. The size of flammable vapor cloud (consequence dispersion index) and the maximum flux of radiation were affected by process parameters more than ambient parameters. Leakage diameter and the vessel pressure were found to have the highest impact on the operational parameters.     

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.     

CFD simulations of ammonia dispersion using “dynamic” boundary conditions

Ammonia is stored in liquid form at ambient temperature and under high pressure. During an accident, ammonia will flash out of the vessel and disperse in the surrounding area. This paper provides a comparison of the results obtained by the FLADIS field experiments and those of CFD modeling by Fluent 6.3. FLADIS experiments were carried out by the Risø National Laboratory using pressure liquefied ammonia. Time series of meteorological conditions as wind speed, wind direction and source strength were determined from the experimentally measured data and used as the inflow boundary conditions. Furthermore, for more realistic simulation of air flow in the computation domain for the desired atmospheric stability, periodic boundary conditions were used on both side boundaries. The initial two-phase flow of the released ammonia was also included. The liquid phase was modeled as droplets using discrete particle modeling, i.e., the Euler–Lagrangian approach for continuous and discrete phases.     

压力容器气体非稳态泄漏模型研究

为计算气体在非稳态泄漏过程中的泄漏率,提高危害后果评估的量化水平,对压力容器失效后气体泄漏过程进行了研究。基于现有的初始泄漏率模型,结合实际泄漏过程中压力容器内各项状态参数的动态变化规律,构建气体非稳态泄漏模型,并通过计算实例进行分析和验证。结果表明,该模型可计算压力容器气体非稳态泄漏过程中(包括音速泄漏阶段和亚音速泄漏阶段)任意时刻容器内的各项状态参数值和孔口处气体的平均泄漏率;同时,对于储存压力较高(大于3.0 MPa)的容器,提出近似计算总平均泄漏率的2种简化方法。     

基于概率神经网络的液氨汽车罐车复合故障诊断

故障诊断在保证危险化学品汽车罐车运输安全方面具有重要意义。从国内交通运输安全的实际要求出发,依据液氨汽车罐车的结构特点及国家法律法规的要求,比较全面、系统地分析了液氨汽车罐车故障特征的相关参数,并将其作为概率神经网络的输入结点。根据实际可能发生的故障分类模式,考虑到故障诊断的容错能力和自适应能力,提出了基于概率神经网络的复合故障诊断模型。利用指标参数作为网络训练样本,对未知故障模式进行诊断,并以广西地区压力容器检验所液氨检测数据为例进行说明。理论分析和实例计算表明,该模型物理概念清晰,计算结果合理,精度较高,在危险化学品汽车罐车故障诊断中有很好的适用性。该项工作可为我国危险化学品汽车罐车故障智能诊断的深入开展提供参考依据。