外文翻译原件.docx

中国石油大学（华东）毕业论文外文翻译译文名称学生姓名：陈思杰学 号：07045201专业班级：安全工程07-2指导教师：朱红卫2011年6月24日This paper is intended to simulate the consequence effect when LNG is released to the surrounding area and develop an emergency plan based on the results of consequence analysis of Liquefied Natural Gas(LNG)facilities. The primary focus of the paper is the effect calculation of accidental and intentional release of LNG. In accordance with increasing demand for LNG which approximates to 20.5 trillion cubic feet by 2010,the need and importance of safety analysis for LNG terminal to the surrounding area are realized.LNG facilities, worldwide, including terminals are in need of off-site risk analysis as well as on-site risk analysis. In this paper, we simulate the heat radiation and behavior of vapor cloud flow resulting from LNG leak or spill using consequence estimation simulators CARM(Consequence Assessment and Risk Management)and PHAST using unified dispersion model by DNV. This would result the estimation of the effect zone based on which are effective strategy to prevent and mitigation the accident is proposed. From the results of the simulation, we seek to propose a strategy to reduce the risk level, which also developing adequate prevention/mitigation procedure that would raise the level of safety in LNG terminalsKey words liquefied natural gas terminal , consequence analysis ,possible hazards vapor cloud behavior mitigation plan.1 introduction natural gas imports totaled 34876 bcf(billion cubic feet) and accounted for 15.6 percent of U.S consumption in 2004 .gross natural gas imports to US .and the rest are imported from Algeria.Australia Malaysia ,Nigeria ,Oman, Qatar and Trinidad and Tobago .Imports from Canada totaled 3.689.8bcf,a 5.2 percent increase from the 2003 level of 3.5088 bcf .according to the increase slightly to 20.5tcf(trillion cubic feet) in 2010 and 21.9 tcf in 202512 . figure 1 shows natural gas import and export activity over the past 17 years 3.as seeing form the date, the consumption and production rate of LNG will be high and l LNG will be use for various purposes for commercial, residential and power supplies .with the growth of the LNG industry since the early 1960s, the safety issues of LNG began to be genrealized in 1944,one of the first commercial LNG plants failed with catastrophic results, delaying LNG technology development for almost 20 year. Nevertheless the potential of wide and high consequence of accident, its demand will increase highly 7.so LNG facilities in the world including terminal sare in need of off-risk analysis as well as the on-site one ,so ,most governments over the world require LNG terminals tit submit proper emergency plans through off-site analysis as well as on-site risk analysis. commercial LNG liquefaction plants and carrier transportation systems have been in operation since 1964.and 4 LNG marine terminals were BUILT in the United States between 1971 and 1980 :Lake Charles, Elba Island, Georgia, Cove Point，Maryland and Everett, Massachusetts. Among the total 244 cargo,59cargos through Cove Point and 41 cargos through Lake Charles,67 cargos through Everett, 77 cargos through Cove Point and 41 cargos through Elba Island in 2004.moreover4-8 new LNG terminal sites are under consideration and for construction.this paper focuses on LNG carrier and terminal facility operation which involved handling cargo and presents estimated consequence potentials for the various scenarios. Therefore, we are going inthe LNG terminal last few decade ,and by considering computational simulation of the hazards that may happen in operation,storage and unloading process,we can calculate and identify the impact area for the release of hazardous materials. And we will propose and recommend the proper and reasonable prevention procedures and strategies to reduce the risk level for the possible accidents through the quantitative risk assessment for specific source of risk .The procedure to estimate the hazard in the LNG terminal is presented in Figure 2.2.PRIOER TIES OF LNG AND PEGULATION 2.1 Property and behavior of LNG LNG is produced by cooling natural gas to approximately -162 at atmospheric pressure. It is stored in insulated tanks of vapor pressure slightly above atmospheric pressure. LNG mainly contains 95%-97% methane, while the rest is a combination of ethane ,propane and other heavier gases.LNG occupies less than one six-hundredth the volume of natural gas at 15 and atmospheric pressure ,making it is economically possible to transport large volumes by sip. LNG is a cryogenic liquid, and is capable of causing extreme thermal effects .It can freeze living tissue exposed to it for more than a few seconds, and can cause the embrittlement and subsequent failure of structural materials such as carbon steel used as material of pipe and other equipment.LNG does not pose a strong hazard unless it is accidentally released in an uncontrolled manner form its specially designed cryogenic containment system. When accidentally released into the environment, it absorbs heat from its surrounding and convert its gaseous form, producing a cold, heavier-than-air, cloud of vapor4.In the initial phase of vapor cloud dispersion, after initial rapid expansion of vapor with its momentum, gravity forces spread the heavy, dense cloud. During this phase the cloud may spread both upwind and downwind. Within a short period of time, the entire cloud starts moving downwind in respond to wind force. As the cold natural gas cloud moves along the ground, it entrains air and become warmed and diluted. Finally large portions of the cloud may become flammable when the methane -air mixture is in the range of 5 to 15 percent by volume. In the second phase of the gas phase of gas cloud dispersion, turbulent forces at the edge and upper surface of the cloud tend to readily dilute the methane -air mixture to concentrations below the lower flammability limit, shrinking the cloud as it moves downwind, until apoint is reached at which no flammable vapor remains. An LNG spill may result in a fire, either at the moment of a spill or after a vapor cloud has formed from the LNG pool. The size of the fire is directly related to the surface area of the spill.LNG vapor confined in a building, conduit or other closed space can explode.2.2LNG processA simplified Process flow diagram of the LNG terminal. including a cargo tank, and related machinery is shn in Figure 3.LNG terminal are designed and constructed to meet codes such as NFPA 59A,US DOT 49 CER 193 and EN 1473.LNG is transferred from the carrier in to the LNG storage tank. Using the carrier s internal pumps, which are sometimes supplemented by stationary booster pumps located at the terminal. During unloading operations, flash and boil-off gas is returned from the tanks to the ship by blowers, compressors or pressure differential. Generally, LNG is vaporized using heat source such as natural gas, seawater or process water. Each tank in this system is equipped with the necessary LNG filling and discharge connections, LNG spray cooling inlet, safety relief valve, liquid level gauge and temperature sensors. The LNG connections to the tanks are connected to the LNG cargo headers which are essentially manifolds for allowing vapor and liquid transfer to and from the tanks .2.3 Safety RegulationDepartment of Transportation and the Federal Energy Regulatory Commission are responsible for the regulation of onshore LNG facility siting (49 U.S.C 60203) such as kind and use of facility ,existing and projected prevention capabilities near the location ,natural physical aspects of the location ,medical ,law enforcement and fire prevention capabilities near the location that can cope with a risk caused by the facility and need to encourage remote siting .The FERC implements its authority over onshore LNG terminals through the agency s regulation at 18FERC s requirements include detailed site engineering and design information, evidence that a facility will safely receive or deliver LNG, and delineation of a facility s proposed location 5.The siting provision in 49 CFR 193 incorporate by references standard 59A from the National Fire Protection association 6.NFPA 59A requires thermal exclusion zones and flammable vapor-gas dispersion zones around LNG terminals.3.POSSIBLE CAUSES OF THE ACCIDENT IN THE LNG TERMINAL The potential mechanisms for causing an accidental and intentional LNG release have been categorized as either non-operational or operational events. The types of potential accidents within each of these categories are described below .3.1Non-operational accidents Earthquakes, hurricanes, air craft crashes, adjacent fires, sabotage and terror are events which could result in large amounts of LNG release in terminals. But earthquakes are not expected to have an effect on the carriers at sea .Hurricane warning systems are sufficiently advanced to provide the LNG carrier with ample time to secure safe anchorage away from probability of such an event is very low(annual probability less than 1 in 100million ) that is precludes further detailed consideration .A large fire at the terminal should not damage an LNG carrier since water spray systems will be installed on the carrier to protect it from fire .3.2 Operational accidentMarine accident statistics from basis for predicting the probability of various of marine accidents in LNG facility .Marine accidents are typically categorized by the principal initiating event. Various causes of accident arise from the stage of operation in the facility .The major accident initiating events are Fire, Explosion in tank terminal, structural failure, collision, ramming and grounding .Since LNG is a completely contained cargo, fire and explosion can occur only of the LNG escapes its normal confinement through equipment failure due to malfunction, human error ,improper design or external forces. The frequency of identified failure modes can be estimated by experience history of LNG and similarly flammable cargos.4HAZARD IN THE LNG TERMINALThe potential mechanisms that could be lead to an accidental or intentional LNG release have been categorized. the results of a potential LNG spill on water or land are described below8.4.1Thermal Damage Once LNG is released from a tank or carrier, it can result two kinds of consequences. If it encounters ahead source and ignites immediately, large pool fire ensues in the vicinity of the release point. The potential damages caused by a pool fire are essentially resulting in intensive heat radiations emanating from the LNG fire, The magnitude of the heat radiation and the area subjected to the heat radiation are dependent on the coverage area and-depth of the LNG spill,And there is relationship between spill area and spill volume with the total spill time as a parameter. By reducing size of the fire a significant reducing of radiation on distant objects is achieved. It would help limiting the area subjected to potential fire damage and the problem that ensue from an expanding fire. The effective heat radiation released from the fire center, within which there is a hazard to people is 4KW/m2 for peopl,1.5kw/m2for continuous exposure and 37.5kw/m2 for property4,It is natural that ultimate hazard from an LNG spill is dependent upon the capabilities of al protection and mitigation system and device, not upon the capability of the extinguishing systems alone, Storage system permits the capability of placing reliable leak detection equipment with automatic actuation of hazard control equipment directly to the affected area. Fire resulting from larger LNG spills can be controlled because of the reduced fire base area and the ability to concentrate the firefighting effort on a smaller area .Possible effect of the LNG fire is combustion and thermal damage and LNG /fireball. Combustion resulting from LNG spill may results in thermal and /or pressure loading .We use the criteria to calculate the thermal damage such as 4kw/m2 are a commonly used value for establishing fire protection distance for people and 37.5kw/m2 may cause significant damage to structure, equipment and machinery .Ignition time is important to the assessment of the type and extent of thermal radiation from LNG spill. In case of LNG/Fireballs, Ignition of a vapor cloud will cause the vapor to burn back to the spill source. Combustion of natural gas with low reactivity usually progresses at low velocity, it rarely causes fireball. But it may cause flashy fire.4.2Explosion Hazard If the flammable vapor cloud evolving from an LNG spill reaches an enclosed area ,as it is carried downwind, the probability for a gas explosion exists. The damage caused by such a gas explosion is usually limited to the enclosed are itself .The possibility of sustaining a detonation through the flammable cloud is too remote to consider realistically. The over pressure generated by a gas explosion in an enclosed area is subject of considerable variation. Overpressure damage normally does not extend beyond the immediate vicinity of the enclosed area. On an LNG vessel, the control rooms which have been located within the storage area are the most susceptible to vapor accumulation .Other machinery spaces and areas of human occupation are aft of the storage area and do not have the same potential for damage propagation simply because these areas are farther removed from the storage area. Furthermore, many of these aft spaces have the ability to isolate themselves by restriction of air intake vents. The maximum areas surrounding an LNG release which can be subjected to the various types to the various types of damage consequences described earlier can be estimated for any LNG release magnitude. An explosion hazard may give rise to two types of effects namely; LNG/Air explosion and rapid phase transition9.Confined fuel/air cloud might occur explosion when a rapid acceleration in burn rate may occur. And when LNG is suddenly heated by contacting a warm liquid such as water, explosive boiling of the LNG can occur, resulting in localized overpressure released.4.3 Cryogenic hazardUnignited and ignited LNG spills onto carbon steel surfaces can cause steel failure by reducing the steel temperature below its embrittlement temperature. Cryogenic damage to deck plate and pipe support structures would create the potential for propagation of a relatively small LNG release into a much large r accident .Scenarios have been developed which postulate LNG release into a much larger accident .Scenarios have been developed which postulate LNG running through brittle fractures into below deck areas to collect and pose an explosion problem as the LNG vaporizes and the normay inert atmosphere is diluted with incoming air. While this propagation due to brittle fracture of pipe supports approach reality. However, the actual extent of cryogenic fracture and its effect on structural members has not been quantified. While every reported cryogenic spill on LNG vessels has produced brittle fracture to protected carbon steel plates, the extent of the brittle fracture has not been well documented .And the detail possible effect for LNG spill is asphyxiation , cryogenic burn and structural damage .Methane ix a simple asphyxiant, but has low toxicity to human, so large vaporizing LNG in the air might be enough to present asphyxiation hazard to the ship crew, pilot boat crew, emergency response personnel and others. And LNG liquid can cause cryogenic burn to personnel and may damage on the integrity of many steels and common ship structural connection. 5.ACCIDNT SCENARIO FOR CALCULATING THE CONSEQUENCE IN THE LNG TERMINALIn this paper, we consider sever accident based on the accident type and magnitude of possible effect. The accident scenarios to calculate the consequence effect of an LNG release divided into two broad categories;(1) continuous release with a variety of hole size on the carrier and LNG tanker in terminal in case of accidental cause, and(2) continuous release at the carrier and LNG tank in terminal in case of Intentional cause. 液化天然气接收站的安全分析侧重于意外和故意泄漏后果计算本文的目的是模拟当液化天然气泄露排放到周边地区时的后果影响并根据对液化天然气（LNG）的基础设施的后果分析建立应急预案。本文的主要焦点是偶然的，蓄意的液化天然气释放效应的计算。随着液化天然气的需求不断增加，到2010年大约到二十万五点零零零亿立方英尺，液化天然气接收站对周边地区安全分析的需要和重要性分析得以实现。液化天然气的设施，包括终端需要场外风险分析以及现场的风险分析。在本论文中，我们模拟了热辐射和蒸气云从液化天然气泄漏或溢出产生的流量行为的后果并使用模拟器CARM（后果评估和风险管理）进行估计，并通过DNV PHAST使用统一的扩散模型。这将有利于对估计的影响区提出有效的战略去防止和减轻事故。从模拟的结果，我们力求提出新的策略以降低风险水平，这也制订适当的会提高水平安全的液化天然气终端的预防/缓解过程。关键词：液化天然气接收站，后果分析，可能危害蒸气云行为的缓解计划。1简介天然气进口总量为34876亿立方英尺（十亿立方英尺）并且在2004年占美国天然气总消耗的百分之15.6。进口天然气对美国非常重要。其余是从阿尔及利亚进口。澳大利亚马来西亚，尼日利亚，阿曼，卡塔尔和特立尼达和多巴哥。加拿大的进口总额为3.689.8亿立方英尺，从2003年的3.5088亿立方英尺的水平增加了百分之5.2。根据从2010年20.5万亿立方英尺（万亿立方英尺）微升到2025年的21.91 2万亿立方英尺。过去17年3图1显示了天然气进口和出口得活动。如同表格显示的数据，液化天然气消费量和生产速度会提升并且液化天然气将用于各种用途为商业，住宅和电力的供应。自20世纪60年代初随着液化天然气业增长，在1944年液化天然气的安全问题开始被重视，第一批商业液化天然气厂以灾难性的后果失败，这大大延缓液化天然气近20年的技术发展。尽管存在着很高很大的事故后果潜力，但其需求量将持续增加7。因此，世界上拥有液化天然气终端设施的需要把风险分析以及现场考察，因此，在世界大多数国家的政府要求液化天然气终端通过适当的应急计划进行的远距离的分析以及现场风险分析。LNG液化厂和商业承运人运输系统已在1964年开始运作。海运码头和4个液化天然气在美国分别建于1971年和1980年：查尔斯湖，厄尔巴岛，格鲁吉亚，科夫波恩特和41货物通过查尔斯湖，67货物通过埃弗雷特，通过科夫波恩特货物77和41厄尔巴岛货物通过2004。此外4-8新的液化天然气接收站的网站正在考虑和建设。本文重点介绍液化天然气运输船和终端处理设施的运营，涉及货物，并提出的各种可能发生的情况的后果分析。因此，我们要在液化天然气接收站最后的几个十年里，运用计算机模拟可能发生在操作，储存和装卸过程中的危害，计算和确定的有害物质释放的影响区域。我们将建议，并建议适当的，合理的预防程序和策略，通过对钛降低风险的具体来源定量风险评估为可能发生的意外风险水平。2.PROPERTIES液化天然气及规例2 .1属性和液化天然气的行为液化天然气是通过在常压下冷却至约-162的天然气。它存储在蒸气压稍微高于大气压力的保温储罐中。液化天然气主要包含95-97的甲烷，其余为乙烷，丙烷和其他更重的气体组合。在15个标准大气压力，液化天然气占不到天然气体积的1/600。，这使的其在经济上是可以通过SIP大量运输。液化天然气是一种低温液体，他能够造成极端的热效应能量。它可以在几秒的时间里冻结暴露的活体组织，并能引起如作为管道和其他设备使用的材料和碳素钢的脆性失效。液化天然气并不能构成强大的危险，除非它是在一个偶然的形式下不受控制地释放方式组建其特别设计的低温密封系统。当意外释放到环境中，它从周边吸取热量并转换器气体形式，形成一种比空气重、冷的蒸汽云。在蒸气云扩散