An overview of emergency relief system design practice

Cost effective loss prevention requires an optimizing strategy to prevent, moderate (relieve) and contain runaway reactions. Ensuring that an emergency relief system design will either avoid or accommodate two-phase vapor-liquid flow is of particular importance. Use of adiabatic runaway reaction test information in combination with digital computer simulation is a powerful method to design an emergency relief system.     

Design charts for two-phase flashing flow in emergency pressure relief systems

The design charts of this paper apply to the high velocity flow of a boiling liquid and its vapor during two-phase emergency pressure relief events. These charts are used to size relief system components to handle a given minimum relief flow requirement. This flow requirement is determined by computer simulation programs such as that described in [1], or by special-case models [2, 3, 4]. Though intended for use in sizing pressure relief systems, the charts are applicable to high-velocity flashing flow problems.     

Emergency pressure relief discharge control by passive quenching—update

A recent runaway reaction emergency relief system design includes a passive quench tank to collect and contain the two-phase emergency relief discharge. This avoids the release of a large vapor cloud to the atmosphere and the attendant flammability and toxicity hazards. The feasibility of quenching is demonstrated with small scale experiments. A pressure relief simulation model is shown to accurately reproduce the observed temperature and pressure profiles in both the reactor and quench tank during relief. The model is then applied to the design of a full scale system. Quench system design considerations are discussed.     

Relief system design scope of CCPS effluent handling guidelines

The forthcoming CCPS Guidelines for Effective Handling of Emergency Release Effluents includes the methodology for defining effluent flow rates and characteristics during emergency pressure relief event. The intent is to provide the user with relief systems in a typical process unit without requiring expert assistance or access to other documents. Cases requiring special design training and methodology due to combinations of multi-phase, multi-component, reactive, geometric and thermodynamic complexities are identified and illustrated in the Guidelines. However, the complete design technology for such cases is beyond the scope of these Guidelines; reference is given to applicable documents.     

Measurement of flow resistance of rupture disc devices

Present codes and practices for the design of relief systems in which rupture discs are used are based either on non-typical system configurations or on “rule of thumb” default values of rupture disc flow parameters. There is a need to develop code methods and common practices based on actual relief system configurations, as well as test methods for determining the actual flow resistance of specific rupture disc devices. The methodology reported here is appropriate for these needs.     

Design and sizing of knock-out drums/catchtanks for reactor emergency relief systems

Sizing criteria and design procedures for knock-out drums and catch tanks used in reactor emergency relief systems.     

Emergency relief vent sizing for fire emergencies involving liquid-filled atmospheric storage vessels

For large atmospheric vessels the potential occurrence of sufficient liquid swell resulting in two-phase flow is of special importance. Based upon an extension of analytical work it would appear justifiable to ignore two-phase flow effects for non-foamy systems.     

The use of spreadsheets in modelling accidental releases of toxic chemicals

Many hazardous industrial chemicals are stored as liquidfied compressed gases. To evaluate the possible consequences of a pipeline rupture, hose break, or tank puncture, the safety or process engineer needs a means to estimate the two-phase (liquid and gas) flow rate. Recent technical advances by the American Institute of Chemical Engineers Design Institute of Emergency Relief Systems (DIERS) have produced methods that can be used to compute the two-phase flow rate. These methods are simple and can be completed using a personal computer and a standard spreadsheet program such as Excel (Macintosh) or Lotus (DOS based). This paper presents the two-phase flow rate calculation method and shows how spreadsheets can be used for these calculations.     

The role of instrumentation and process controls in minimizing accidental releases

Most accidental releases are the result of either mechanical failures or measures taken to prevent such failures, such as, venting through emergency vents, relief valves, or rupture discs. Where the mechanical failure is the result of defective materials, inadequate design, or external factors, little can be done by means of instrumentation to prevent the release. It may be possible, however, to reduce the flow. Many failures are due to process upsets such as overpressure, internal explosions, and runaway reactions. The probability of these failures occurring can be substantially reduced by proper instrumentation.     

Application of the DIERS methodology to the study of runaway polymerization: Validation of the DIERS methodology using blow-down tests

The Design Institute for Emergency Relief Systems (DIERS) and more recently the DIERS Users Group have been investigating various aspects of emergency relief for more than 12 years. The DIERS programs have given rise to an in-depth understanding of the basic mechanism of how runaway thermal reactions are safely vented. In concert with the development of the understanding of the venting mechanism, DIERS also developed experimental procedures and computational techniques for estimating emergency vent sizes.     

无源控制多相计量技术在油井计量中的研究应用

针对目前分离器计量和人工化验含水不能满足单井计量需要以及现有多相计量方法存在的不足,开展了对管式气液旋流分离技术、气液分离无源控制技术及相关配套计量工艺技术的研究,该技术经现场应用,取得了理想效果,为目前计量站油井多相计量工艺的升级换代提供了选择。     

Persistent myths about emergency seed aid

Seed interventions are the major agricultural response during emergency and recovery phases of humanitarian relief. They are implemented by diverse agencies, and widely promoted: for instance the FAO alone managed 400 such projects between 2003 and 2005. However, seed aid suffers from a lack of critical attention, perpetuating widespread myths among practitioners, policymakers, and the larger humanitarian community. This paper challenges five predominant myths about seed aid: (1) seed aid is needed whenever food aid is; (2) seed aid can do no harm; (3) disasters wipe out seed systems; (4) effective implementation is a straightforward logistical exercise, and; (5) improved seed is the best form of aid. These myths are juxtaposed with recent empirical work across a range of countries, particularly in Eastern and Southern Africa. The perpetuation of such myths highlights a serious absence of scrutiny of emergency seed aid, and helps explain why such aid is repeated year after year in many sites, with little apparent positive effect. The paper argues that the invisibility of seed aid is a major cause for the lack of oversight and concludes that donors and farmer beneficiaries must become centrally involved in seed aid governance.     

突发性水污染事故应急管理体系研究

通过对发达国家突发性水污染应急管理体系经验的总结以及中国松花江污染事故的案例分析,归纳了中国现有突发性水污染应急管理体系存在的不足之处,从法制建设、机构协调、事故预警和信息公布等4个方面提出了建设性意见。     

Process safety evaluation applying DIERS methodology to existing plant operations

The DIERS methodology can be used to quickly assess the relief capacity envelope for a collection of existing process vessels accounting for both vapor and gassy systems. Easy-to-use vent sizing nomograms and PRESS sheets are proposed that can be completed by the process engineering, the process chemistry and the process safety departments. A vessel volume-vent size diameter relationship is also developed using the source term based on fire exposure to cover a reasonable range of credible upset scenarios. In this way the adequacy of existing relief systems can be quickly surveyed for potential trouble sources—“outliers”—warranting further evaluation and corrective action.     

热泵直供采暖两相流毛细管网性能研究

通过在用户自定义程序增加两相流动中质量源项和能量源项的方法,建立了毛细管网内气-液转化的CFD计算模型,对小管径光滑铜管内R22的冷凝性能进行研究。根据CFD模型,计算了不同气相进口流速下R22蒸汽的冷凝过程。得到了压力损失、冷凝系数和流速的关联曲线。对小管径毛细管网辐射末端的设计提供了理论依据,对制冷剂流速选择有一定指导意义。     

图像浮雕算法及其在防伪印刷中的应用

图像浮雕技术是指通过一种特殊处理,改变二维平面图像中的有效内容、图像边缘或者特定区域的颜色值,增强图像立体显示效果的技术。基于孔斯曲面理论,本研究提出了一种新的矢量图像浮雕算法,即通过矢量线条的局部变形来再现图像雕刻般凹凸效果。实验表明,通过上述方法得到的图像浮雕图案克服了现有算法中固定浮雕角度偏移的缺陷,所表现的浮雕凹凸效果更加细腻,既能达到美观的艺术效果,同时作为一种非常重要的版纹防伪元素在防伪印刷中有着广泛的应用价值。     

Hydrodynamic aspects of venting for vessels containing viscous fluids

Nine depressurization experiments for vessels containing water, freon-114 and high viscosity fluids have been analyzed. These experiments were carried out at different plants and provide information about the dependence of the depressurization process on the size of the vessel, the type of vent installed, and the initial conditions. The differences of venting into the atmosphere or venting into a catch tank have been also examined. The accuracy of the two-phase flow model used for the analysis of these experiments has been demonstrated by comparisons with steady state data referring to co-current liquid/vapor flow as well as to batch type of flows, where the liquid phase is stagnant.     

水体中阳离子表面活性剂测定方法的研究进展

对阳离子表面活性剂的常用检测方法:分光光度法、毛细管电泳法、高效液相色谱法、两相滴定法、电化学传感器分析法、极谱法等进行了综述,提出了水体中阳离子表面活性剂检测方法的发展方向,即信息化、智能化、微型化。     

基于颗粒动力学的高炉风口焦炭行为仿真研究

焦炭在风口回旋区运动、燃烧,其行为对回旋区的活跃程度产生影响,对高炉起着非常重要的作用,但受到实验手段的限制,难以对其进行直接的测量研究。应用颗粒动力学将焦炭颗粒视作拟流体,采用欧拉双流体理论构建了气固两相流风口回旋区仿真模型,并验证了该模型的正确性。通过该模型分析了回旋区内焦炭的运动规律和燃烧后气体成分的变化,发现风口前端回旋区外围的环形带是焦炭进入回旋区的主要位置;O2浓度沿风口中心线向炉内逐渐降低,CO2浓度先增加后减小至零,CO浓度逐渐增加至稳定。     

Netzausbauplanung unter Berücksichtigung probabilistischer Einflussgrößen

The present network expansion planning is performed by simulating extreme scenarios in order to proof the security of energy supply. This procedure is associated with high investment costs for equipment which is only needed a few hours per year. Planners have to consider uncertainties and prediction errors for the creation of the extreme scenarios due to the long economic life time of the equipment. The consideration of these influencing factors becomes very complex due to increased utilization of renewable energy sources and frequent changes in the unit commitment of conventional power plants. In contrast to classic load flow methods probabilistic load flow calculation considers the static behaviour of the loads, renewable energies and the power plants instead of only discrete values of nodal powers. These characteristics can be described by probabilistic density functions of load and generation mapped with a probabilistic load flow calculation into a probabilistic density function of the state variables of the energy system (as nodal voltages or line currents). This article presents an overview about existing methods of probabilistic load flow calculations and introduces a newly developed method. The characteristics and the applicability of these methods are verified and the computational burden is analysed exemplarily. Necessary extensions for the mapping of real energy systems and possible approaches for this are presented. The potential and the impact of probabilistic network expansion planning are discussed.