Gas leakage consequence modeling for buried gas pipelines

One of conservation transfer methods for such widely-used gases as natural gas and hydrogen is buried pipelines. Safety of these pipelines is of great importance due to potential risks posed by inefficiencies of the pipelines. Therefore, an accurate understanding of release and movement characteristics of the leaked gas, i.e. distribution and speed within soil, the release to the ground surface, the movement of hydrogen gas through the ground, gas underground diffusion, gas dispersion in atmosphere, and following consequences, are very important in order to determine underground dispersion risks. In the present study, consequences of gas leakage within soil were evaluated in two sub-models, i.e. near-field and far-field, and a comprehensive model was proposed in order to ensure safety of buried gas supply pipelines. Near-field model which is related to soil and ground and its output is the gas released at different points and times from ground surface and it was adopted as input of far-field sub-model which is dispersion model in atmosphere or an open space under the surface. Validation of near-field sub-model was performed by the experimental data obtained by Okamoto et al. (2014) on full-scale hydrogen leakage and then, possible scenarios for far-field sub-model were determined.     

基于资源分类的资源耗竭度及当量系数

资源耗竭潜力因子ADP(Abiotic Depletion Potential)是目前评价产品生命周期资源消耗水平的常用因子,但不够细致全面,存在一定的局限性.考虑到资源特点多样性,将资源分为可再生资源、可回收的不可再生资源和不可回收的不可再生资源3类,并针对性地提出资源耗竭度RDD(Resource Depleon Degree)和资源耗竭当量系数EF(Equivalent Factor)的计算公式,构建评价框架对自然资源耗竭性进行分类评价.将评价方法运用于建筑行业某住宅,得到其物化阶段5种资源消耗水平,验证了该评价方法的可行性及RDD因子相对于ADP因子在资源耗竭评价方面的优越性.     

突发性环境污染事故应急监测分析

随着我国经济水平的提高,人们对生活质量的要求也逐渐提高,因此政府也在逐渐加大经济建设和资源开发力度,力求满足人们对生活水平的要求。但是近年来由于资源开采过多,环境的污染程度逐渐加重,由于各种污染物质的相互作用,突发性的环境污染事故发生的次数也逐渐增多。山西是我国的能源大省,拥有很多重工业的基地,产生了大量的工业污染,对水体、大气以及土地都产生了不同程度的污染,引发了突发环境污染事故的出现。本文立足于山西突发性环境污染事故应急监测的现状,分析了山西省在应急监测上所存在的问题,并提出了相应的解决措施,力求降低突发环境污染事故的影响。     

工艺流程中氨泄漏事故后果分类研究

氨是重要的化工原料和产品,工艺流程中氨主要以氨气、液氨、氨溶液三种状态存在。氨气、液氨、氨溶液理化特性及危险特性不同,可能造成的事故后果类型不同,分别进行三种相态下氨泄漏的事故情景分析。氨气泄漏主要考虑蒸气云爆炸、中毒,液氨泄漏主要考虑沸腾液体扩展蒸气爆炸、蒸气云爆炸、中毒,氨溶液泄漏主要考虑中毒和腐蚀。运用半球模型和高斯模型计算某尿素企业液氨球罐泄漏的危害范围。半球泄漏模型计算方法较简单,但没有考虑氨本身性质及气象条件等因素;高斯模型计算过程较复杂,其计算结果与风速、大气稳定度等条件相关。该两种方法计算结果对预防氨泄漏事故发生和氨泄漏事故预警均具有一定参考意义,如何提高模拟分析的准确度是今后研究工作的重点。     

Quantitative risk analysis of urban natural gas pipeline networks using geographical information systems

This paper presents a novel quantitative risk analysis process for urban natural gas pipeline networks using geographical information systems (GIS). The process incorporates an assessment of failure rates of integrated pipeline networks, a quantitative analysis model of accident consequences, and assessments of individual and societal risks. Firstly, the failure rates of the pipeline network are calculated using empirical formulas influenced by parameters such as external interference, corrosion, construction defects, and ground movements. Secondly, the impacts of accidents due to gas leakage, diffusion, fires, and explosions are analyzed by calculating the area influenced by poisoning, burns, and deaths. Lastly, based on the previous analyses, individual risks and social risks are calculated. The application of GIS technology helps strengthen the quantitative risk analysis (QRA) model and allows construction of a QRA system for urban gas pipeline networks that can aid pipeline management staff in demarcating high risk areas requiring more frequent inspections.     

CNG加气站事故后果分析方法研究

根据CNG加气站系统运行的实际情况,将CNG加气站中易发生泄漏的设备分为管道阀门、挠性连接器、压缩机、储气设备、放散管5类。建立了CNG泄漏的事件树,将CNG加气站的事故后果类型概括为喷射火、闪火、蒸气云爆炸。总结了CNG加气站事故后果的计算模型,采用美国环保局的ALOHA软件确定事故后果的影响范围。综合运用该两种方法对喷射火和蒸气云爆炸的事故案例进行对比研究,结果表明,计算结果基本一致。该两种事故后果分析方法为CNG加气站安全管理和安全规划提供依据。     

天然气净化厂管道泄漏H2S毒害后果影响因素数值分析

为定量评估高含硫天然气开敞空间泄漏过程中风速、风向、泄漏速度、泄漏方向对毒害后果的影响,以天然气净化厂管道泄漏为例,采用正交实验设计方法设计实验场景,基于CFD进行泄漏扩散仿真实验,以吸入剂量、毒害面积、最大毒害面积到达时间、毒害体积、最大毒害体积到达时间作为毒害效应指标,分析不同因素对毒害后果的影响,并提出后果控制建议。研究结果表明:采用CFD方法进行泄漏扩散仿真能够还原泄漏扩散过程;利用正交实验进行影响因素分析可以节省实验资源、获取准确结果;风向和风速对各后果指标均比较敏感,在天然气净化厂建设过程中应着重考虑风的影响。仿真与正交实验结合的方法能够有效评估毒害后果影响因素的敏感性,可为毒害气体泄漏风险防控提供指导。     

Environmental evaluation for workplace violence in healthcare and social services

PROBLEM: Federal policy recommends environmental strategies as part of a comprehensive workplace violence program in healthcare and social services. The purpose of this project was to contribute specific, evidence-based guidance to the healthcare and social services employer communities regarding the use of environmental design to prevent violence. METHOD: A retrospective record review was conducted of environmental evaluations that were performed by an architect in two Participatory Action Research (PAR) projects for workplace violence prevention in 2000 and, in the second project in 2005. Ten facility environmental evaluation reports along with staff focus group reports from these facilities were analyzed to categorize environmental risk factors for Type II workplace violence. RESULTS: Findings were grouped according to their impact on access control, the ability to observe patients (natural surveillance), patient and worker safety (territoriality), and activity support. DISCUSSION: The environmental assessment findings reveal design and security issues that, if corrected, would improve safety and security of staff, patients, and visitors and reduce fear and unpredictability. IMPACT ON INDUSTRY: Healthcare and social assistance employers can improve the effectiveness of violence prevention efforts by including an environmental assessment with complementary hazard controls.     

Study on leak-acoustics generation mechanism for natural gas pipelines

In order to figure out the principles of acoustic leak detection for natural gas pipelines, a study on the leak-acoustics generation mechanism is carried out. The aero-acoustics generation mechanism is analyzed and when leakage occurs the wave equations of sonic sources are developed. The leak-acoustics generated by the quadrupole and dipole sonic sources are then simulated to obtain the laws of the acoustic characteristics. The simulation data are compared with the experimental data to verify the simulation accuracy under variable operating conditions. The results show that the quadrupoles and the dipoles generated by turbulent fluctuations cause leak-acoustics; the main component of pressure perturbations acquired by the dynamic pressure sensor is acoustic perturbations; both the simulation method and the experimental method can be applied to study the leak-acoustics generation mechanism of natural gas pipelines.     

Multi-objective synthesis of a company's supply network by accounting for several environmental footprints

This contribution presents the multi-objective synthesis of a company's supply network by integrating renewables (biomass and other waste, and solar energy) and accounting for several environmental footprints. The synthesis is based on a Mixed-Integer Linear Programming (MILP) problem. A previously developed model by the authors for achieving energy self-sufficiency by integrating renewables into companies’ supply networks has been extended for the evaluation of environmental impacts, such as energy, carbon, nitrogen, and water footprints. The achievement of an energy self-sufficient supply network has been considered whilst significantly reducing environmental impacts.The presented model is applied to multinational poultry-meat producing company. Direct (burdening) and indirect (unburdening) effects that form total effects on the environment are considered for the evaluation of environmental footprints. The results showed significant unburdening of the environment in terms of carbon and nitrogen footprints but, however, higher burdening in terms of the water footprint.     

Developing a risk-based maintenance model for a Natural Gas Regulating and Metering Station using Bayesian Network

During the last decades, the vital role of maintenance activities in industries including natural gas distribution system has cleared up progressively. High costs may induce to reduced maintenance and, in turn, lead to a lower availability and high risk of undesired events. Therefore, a probabilistic model, based on an acceptable level of risk, is required to avoid under and over estimation of maintenance time interval. This paper presents an advanced Risk-based Maintenance (RBM) methodology to optimize maintenance time schedule. Bayesian Network (BN) is applied to model the risk and the associated uncertainty. The developed method can assist the asset managers to work out the exact maintenance time for each component according to the risk level. To demonstrate and discuss the applicability of the methodology, a case study of Natural Gas Reduction and Measuring Station in Italy is considered. Results prove that the most critical components are the calculator and pilots, while the most reliable one is the odorization. Furthermore, the pressure and temperature gauge (PTG), the remote control system (RCS) and the meter are predicted as the components that require less time to transit from minor risk to catastrophic risk.     

液氯储罐瞬时泄漏扩散质量浓度分布规律与中毒后果评价

液氯储罐一旦发生泄漏,容易在大气中快速扩散,其扩散速度受到泄漏量、外界风速等条件的影响。为了研究不同风速和泄漏量对氯气扩散规律的影响,分别在泄漏量为2 kg、5 kg,外界风速为2 m/s、5 m/s的条件下,采用Fluent软件模拟了氯气储罐瞬时泄漏后氯气质量浓度随时间的分布规律,并结合氯气的致死浓度,对氯气扩散区域最大质量浓度分布及其毒性致命损伤进行了分析。结果表明,氯气扩散初期,云团浓度较高,重气效应比较明显,随时间增加云团逐渐增大。泄漏量越大,氯气的扩散速度和致死区范围越大,毒性致命损伤时间越短;风速越大,致死区的影响距离越大,但致死区的影响时间大幅度缩短,能有效降低氯气的中毒危害。     

A model for the initial stages following the rupture of a natural gas transmission pipeline

Experience shows that, despite the best efforts of the pipeline industry worldwide, pipelines do fail and release their contents to the atmosphere. In the case of below-ground pipelines transmitting natural gas, there is a chance that the release will be ignited, posing a significant hazard to any people in the vicinity. Mindful of this hazard, an international group of gas companies have collaborated over a period of many years on research projects aimed at developing an understanding of how these releases may arise (failure causes), how often they might occur (failure frequency), what type of releases might be produced (failure modes) and what type of behaviour might be produced for each of these modes of release (consequence analysis). This paper has been prepared to describe the mathematical models that have been developed on behalf of this group to assess the initial transient period following the rupture of a buried natural gas transmission pipeline assuming the release ignites immediately. It gives details of the equations used by the different models and it refers to some of the experimental data that has been used in the development of the models. A comparison of the model with the experimental data is provided. This demonstrates that the early stages could have a significant impact when evaluating the harm that could be caused. This provides a justification for developing the models rather than using a simpler alternative that does not take the initial highly transient period into account.     

An optimization of artificial neural network modeling methodology for the reliability assessment of corroding natural gas pipelines

A fast calculation of the reliability is meaningful to the in-line inspection of corroding natural gas pipelines. However, the traditional Monte Carlo simulation(MCS) method is time consuming for the low possibilities of the pipeline failure. The artificial neural network(ANN) is preferable for the complex nonlinear situation. An optimization of artificial neural network modeling methodology for the reliability assessment of corroding natural gas pipelines is proposed in this paper. To reduce the influence of training sets random behaviors on the calculation results, some algorithms are used to optimize the sequence of the training samples and the initial parameters of ANN models. The optimized model is applied to the reliability assessment of a corroded pipe with two successive inline inspections. According to the physical parameters of the pipeline, the trend of corroding pipeline reliability in time is predicted. The comparison between the trained ANN model, the MCS method and non-optimized ANN model shows the advantages the proposed modeling process. The methodology given in this paper is general and it can be applied to evaluate the reliability of other kind of structure safeties in practical systems.     

重型车辆荷载下埋地天然气管道的安全分析

道路下的埋地天然气管道在重型车辆荷载通过时,管道受力一旦达到破坏强度就可能产生安全事故,造成天然气泄漏而引发燃烧与爆炸的危害,需要进行安全分析来判定重载车辆能否安全的通过道路运输。该文用理论计算和实验检测的方法综合起来分析埋地管道的相关力学参数,然后与管道自身的强度参数进行比较,从而判断埋地管道是否破坏。通过实例验证的方法说明了该方法在类似的项目分析中具有适用性和操作性,并提出了分析方法应用的初始条件。该方法可以作为判断埋地天然气管道在重载车辆作用下的一种安全评价方法,在条件允许的情况下可以利用数值模拟的方法进行比较印证,从而得到更为可靠的判断结论。同时,该方法也为埋地天然气管线在重载作用下的保护提供了基础资料,可以在此指导下更有效的保护天然气管线免受破坏。     

毒气泄漏扩散风险的参数不确定性分析

有毒气体泄漏扩散受很多不确定性因素的影响,为了分析和评估影响毒气泄漏扩散的风速和泄漏速率的变化和不确定性,采用蒙特卡罗模拟和基于Wilks公式容许限的非参数统计法,通过抽样计算得到“95/95准则”下的毒气泄漏扩散地面浓度分布,计算了有毒气体泄漏扩散的不同风险等级的影响范围和风险概率曲线。以氨气泄漏事故为例进行实例分析,结果表明,相对于以确定性参数得出的氨气泄漏扩散浓度分布,引入参数的不确定性评估,更能贴合泄漏现场存在不确定性因素的实际情况,更有利于人员的安全和应急疏散管理。     

天然气管道应急体系网络结构优化分析

为达到帮助应急决策机构能迅速高效地完成天然气管道事故应急救援方案和行动的目的,运用UCINET软件对天然气管道应急体系的网络结构进行优化。通过分析应急指挥体系的自组织特性、控制特性和不确定性,参考美国卡特里娜飓风事故的应急救援组织网络,借助UCINET对天然气管道事故应急救援体系中的组织部门程度、接近和中间集中性分别进行相应的计算分析,归纳总结出天然气管道事故应急过程中最重要的组织部门。通过加强重要组织部门的通讯能力,实现对网络结构的优化,为提高部门间的协作能力,快速高效地完成应急救援任务提供支持。     

城市油气管道泄漏爆炸重大案例应急管理对比研究

青岛东黄输油管道泄漏爆炸特别重大事故,引起公众对城市油气管道安全的普遍关注。近年来,城市油气管道事故频繁发生,反映出我国在城市地下管道安全管理方面存在较大问题。基于国内外管道相似事故调研,选取墨西哥瓜达拉哈拉管道泄漏爆炸事故和青岛东黄输油管道泄漏爆炸事故进行对比分析。基于事故致因理论,探究事故发展模式,建立事故链模型。结合应急管理思想,从预警预控、应急处置、评估恢复角度分析事故应急管理过程的共性失误。最后,针对应急管理各阶段共性失误提出防范措施,对提高类似事故的应急管理能力具有一定的参考意义     

高含硫化氢井场公众疏散能力分析方法研究

我国含硫气田存在含硫量高、周边人口稠密、地形复杂等危险因素,如何保证含硫气田周边居民安全疏散成为一个重要的急需解决的问题.针对高含硫气田开发过程面临的公众疏散能力问题,采用毒性负荷判别法作为疏散能力评估的准则,提出一套分析流程,并给出相应的改进措施,形成一整套的复杂地形下高含硫化氢井场公众安全疏散能力分析方法;通过对本方法在现场实际中的应用,在理论和实例分析基础上,发现对高含硫气田井场进行疏散能力评估是可行且非常必要的.     

白集煤矿区域可控循环风系统的理论分析与试验

针对白集煤矿深部采区供风量不足的问题,从技术和经济两个方面论证了该煤矿可控循环风方案的可行性,设计了一套由喷雾降尘装置、过滤装置和冷却降温装置组成的循环风流处理系统.在理论上分析了循环风流中瓦斯体积分数、粉尘质量浓度和其他气体成分在可控循环风系统中变化规律,以及可控循环风系统对主通风系统的影响.通过现场实测,不仅验证了瓦斯体积分数、粉尘质量浓度的变化规律,而且处理后的循环风流品质完全达到<煤矿安全规程>要求,同时对回风流的降温降湿处理,可满足高温高湿矿井工作面对风流温湿度的需求.