Comparison of two schemes for district cooling system utilizing cold energy of liquefied natural gas

Two schemes（scheme Ⅰ and scheme Ⅱ）for designing a district cooling system（DCS）utilizing cold energy of liquefied natural gas（LNG）are presented.In scheme Ⅰ,LNG cold energy is used to produce ice,and then ice is transported to the central cooling plant of the DCS.In scheme Ⅱ,return water from the DCS is directly chilled by LNG cold energy,and the chilled water is then sent back to the central plant.The heat transportation loss is the main negative impact in the DCS and is emphatically analyzed when evaluating the efficiency of each scheme.The results show that the DCS utilizing LNG cold energy is feasible and valuable.The cooling supply distance of scheme Ⅱ is limited within 13 km while scheme Ⅰ has no distance limit.When the distance is between 6 and 13 km,scheme Ⅱ is more practical and effective.Contrarily,scheme Ⅰ has a better economic performance when the distance is shorter than 6 km or longer than 13 km.

Socio-Economic Implication of Nigeria Liquefied Natural Gas (NLNG) Project in Bonny Local Government Area, Rivers State, Nigeria

Notably, the Nigeria Liquefied Natural Gas (NLNG) project is the pioneer Liquefied Natural Gas (LNG) plant in Nigeria, aimed at both the diversification of the petroleum industry and utilization of the vastly flared natural gas resources of the nation. However, large scale energy projects have been known to generate both positive and/or negative impacts. Environmental Management Plans (EMP) have often been the compendium of information on approved mitigations, which normally include activities that could maximize the benefits of the host communities, and it’s not unusual for the Community Development and Corporate Social Responsibility (CDCSR) department of such an organization to be saddled with these contributions. But the activities of Nigeria LNG Ltd.’s CSR department have often been the source of criticism, as well as aspiration for improvement by host communities and other stake holders. This article thus aims to present a comprehensive compendium of NLNG’s CDCSR activities, up to the year 2010, and also highlight the level of satisfaction of the immediate and distant host communities against the level of performance of other donors in the area. Also the arrays of negative socio-economic consequences of the Nigeria LNG Ltd.’s activities were identified based on community perception. The results generally showed that comparatively, NLNG project has made more innovative positive socio-economic and health contributions to its areas of operation than the three tiers of government and other donors (including SPDC and Mobil Producing Nigeria). Surprisingly, agitations against Nigeria LNG Ltd.’s activities have not overshadowed its community development provisions, which have been of major assistance in several communities. There is however a dire need to review several aspects of Nigeria LNG Ltd.’s CDCSR activities, especially in the fulfilment of documented promises, as well as in project conception and community participation, for better completed projects acceptance by indigenous host communities. Conflict management strategies also need to be improved, while the dissatisfaction over benefits in New Finima needs to be urgently addressed.

Distribution and Chain Pattern of Liquefied Natural Gas Industry in China

The production and consumption of natural gas in China has been developing rapidly in recent years.It is expected that the annual growth rate of the demand for natural gas will reach 12% in the next 15 years,and the gas consumption in the primary energy will increase from 0.3% to 10% or more by 2020.However,since the supply of natural gas cannot satisfy the requirements,China has begun to build liquefied natural gas(LNG)terminals in the coastal regions such as Guangdong and Fujian,and solve this problem by importing LNG from foreign countries.LNG needs to be transported by LNG ships from abroad.With the rapid growth of global gas production,the volume of LNG trade also increases,and the interregional production increased from 0.3% in 1970 to 26.2% in 2004.So,we need LNG ships more than before.This article puts forward the distribution of LNG ships and the speculation of the future of LNG transportation based on the studies on foreign LNG production,the LNG trade,the building of LNG ships,the LNG transportation,the chain model of LNG distribution,etc.

GTL or LNG:Which is the best way to monetize "stranded" natural gas?

A large portion of world＇s natural gas reserves are ＂stranded＂ resources, the drive to monetize these resources leads to the development of gas-to-liquids （GTL） and liquefied natural gas （LNG） technologies. LNG has the advantage of having been developed for the past 40 years and having an excellent safety record. GTL on the other hand is another option with substantial benefits, but its development stage and commercial viability are far behind LNG. This paper presents a techno-economic comparison of GTL with LNG, including technical development, plant efficiency, market potential for the products, and capital cost for the infrastructure. The aim is to give an overall view on both LNG and GTL and provide a perspective on the profitability of these two technologies.

Research on the navigational risk of liquefied natural gas carriers in an inland river based on entropy:A cloud evaluation model

Due to the flammability and explosive nature of liquefied natural gas(LNG),an extremely strict process is followed for the transporta-tion of LNG carriers in China.Particularly,no LNG carriers are operating in inland rivers within the country.Therefore,to ensure the future navigation safety of LNG carriers entering the Yangtze River,the risk sources of LNG carriers’navigation safety must be identi-fied and evaluated.Based on the Delphi and expert experience method,this paper analyses and discusses the navigation risk factors of LNG carriers in the lower reaches of the Yangtze River from four aspects(human,ship,environment and management),identifies 12 risk indicators affecting the navigation of LNG carriers and establishes a risk evaluation index system.Further,an entropy weight fuzzy model is utilized to reduce the influence of subjective judgement on the index weight as well as to conduct a segmented and overall evaluation of LNG navigation risks in the Baimaosha Channel.Finally,the cloud model is applied to validate the consistent feasibility of the entropy weight fuzzy model.The research results indicate that the method provides effective technical support for further study on the navigation security of LNG carriers in inland rivers.

COGAS Propulsion for LNG Ships

Propulsion of liquefied natural gas (LNG) ships is undergoing significant change. The traditional steam plant is losing favor because of its low cycle efficiency. Medium-speed diesel-electric and slow-speed diesel-mechanical drive ships are in service, and more are being built. Another attractive alternative is combined gas and steam turbine (COGAS) drive. This approach offers significant advantages over steam and diesel propulsion. This paper presents the case for the COGAS cycle.

大型LNG船再液化设备基座静刚度分析及结构优化

为了保证大型液化天然气(Liquefied Natural Gas, LNG)船再液化设备的基座在设备工作载荷作用下具有较高的抵抗变形能力,提高再液化设备运转过程中的安全性,以大型LNG船用再液化设备的基座所受载荷为基础,进行整个再液化设备的基座结构设计,并基于有限元分析软件进行刚度计算。计算结果表明:在工作载荷作用下,基座抵抗横向和纵向变形的能力较弱,在结构优化加强时,增加结构的板厚对整个基座的静刚度改善作用亚于增加纵向或横向支撑型材。研究结果可为船舶类设备基座结构的设计及加强优化提供一定参考。

大型LNG船用惰气发生器系统特点及其应用

为提高液化天然气(Liquefied Natural Gas,LNG)船与惰气发生器系统的匹配度,基于惰气制取流程,对不同类型惰气发生器的应用范围进行归纳,对大型LNG船用惰气发生器的系统特点、要求和布置准则进行分析,并对不同厂商惰气发生器的结构形式和性能特点进行对比。研究表明:惰气发生器的油耗、整机功率、排量等参数为大型LNG船选型的首要依据。研究成果可为大型LNG船用惰气发生器的选型与应用提供一定参考。

LNG动力船舶修理安全管控

为了提升液化天然气(Liquefied Natural Gas, LNG)动力船舶修理期间的风险管控水平,对LNG燃料的基本特性展开介绍,分析LNG泄漏或失控所造成的危害,并对不同的LNG动力船舶系统的相应维修情况进行对比分析,同时阐述LNG动力船舶维修时存在的主要额外风险及相应风险产生的原因。在此基础上,提出船舶携带LNG修理期间在危险区域和安全敏感区域工作的相应预防措施。研究成果可为LNG动力船舶修理安全管控提供一定参考。

A review of cryogenic power generation cycles with liquefied natural gas cold energy utilization

Liquefied natural gas （LNG）, an increasingly widely applied clean fuel, releases a large number of cold energy in its regasification process. In the present paper, the existing power generation cycles utilizing LNG cold energy are introduced and summarized. The direction of cycle improvement can be divided into the key factors affecting basic power generation cycles and the structural enhancement of cycles utilizing LNG cold energy. The former includes the effects of LNG-side parameters, working fluids, and inlet and outlet thermodynamic parameters of equipment, while the latter is based on Rankine cycle, Brayton cycle, Kalina cycle and their compound cycles. In the present paper, the diversities of cryogenic power generation cycles utilizing LNG cold energy are discussed and analyzed. It is pointed out that further researches should focus on the selection and component matching of organic mixed working fluids and the combination of process simulation and experi- mental investigation, etc.

Research on Temperature Field and Thermal Stress of Liquefied Natural Gas Carrier with Incomplete Insulation

The insulation of membrane type liquefied natunal gas （LNG） carrier is composed of plywood boxes filled with perlite. Within the service period, considering of the effects of load conditions, such as sloshing, wave load, it is possible to have some damage of the plywood box, leakage of perlite, and failure of the insulation box. LNG carrier without whole protection of effective insulation is dangerous. Hull structure is extremely fragile when exposed to ultra-low temperature. In order to solve these problems, firstly a study on insulation boxes＇ character and work condition is carried out and some presuppositions of partial disabled insulation are put forward. Secondly the thermal system of LNG carrier is analyzed to find out an effective way to simulate the thermal action of close air between outer and inner hull. Then a calculation about temperature field and thermal stress is done by MSC/PATRAN＆NASTRAN. At the end it is concluded that LNG carrier with incomplete insulation is dangerous and needs to be avoided.

Influence of Excitation Frequency on Slosh-Induced Impact Pressures of Liquefied Natural Gas Tanks

Liquid sloshing phenomena in No.2 tank of 140 km 3 liquefied natural gas (LNG) carriers have been studied numerically and experimentally.The scale of the model tank was selected as 1/55.9.Roll and pitch motions were tested.For measuring impact pressures,seventeen pressure sensors were installed on the tank model.A large number of excitation frequencies and filling heights were investigated.The experimental results showed that when the frequency of tank motion is close to the natural frequency of fluid inside the tank,large impact pressures may be caused.Resonance frequencies and maximum impact pressures of different filling height were presented.Among all the experimental situations,the maximum impact pressure always occurs at the place near 70% height of tank where should be especially concerned.A computational fluid dynamics (CFD) model was developed to simulate the sloshing in the tank.The model was based on the Reynolds-averaged Navier-Stokes (RANS) equations,with a standard κ-ε turbulence model.The volume of fluid (VOF) method was used to predict free surface elevations.Dynamic mesh technique was used to update the volume mesh.Computations for pressure time histories and peak pressures were compared to experimental results.Good agreement was observed.

LNG加注趸船的池火危险距离分析

液化天然气(LNG)加注趸船是一种适用于为长江上航行的LNG动力船实施燃料补给的工作船。低温损伤和火灾损伤是LNG泄漏后产生的对船舶造成的主要风险。为了控制LNG加注趸船的风险,论文分析了LNG加注趸船泄漏后可能产生的低温重气扩散、快速燃烧、喷射火、池火等不利后果;由于池火的风险较高,因此需要分析为趸船设计布置的池火危险距离。论文还讨论了人员、船上钢结构建筑物及储罐的热辐射通量接受准则,选取了合适的热辐射通量接受准则并且用于论文中的计算。热辐射危险距离计算采用简化的点源模型和实体火焰模型;以加注口泄漏LNG为例,当泄漏量为0.5m3时,计算了在尺寸为1m×1m×0.6m的立方体的集液盘中发生池火所应采取的危险距离布置。计算结果表明:在不采取热辐射隔绝措施下,对于人员露天作业的危险距离为14m,对于控制室等建筑物的危险距离为12m,对于储罐的危险距离为9m;并且建议应采用可考虑环境因素的实体火焰模型来计算池火危险距离。

考虑多米诺效应的LNG事故后果定量风险分析

为提高液化天然气(LNG)事故后果定量风险分析(QRA)的准确性,在分析中考虑多米诺效应对后果(个人风险)的影响。个人风险计算步骤包括确定初始事故,选择合适的模型计算初始事故产生的热辐射和超压值,计算事故周边设备的损坏概率以及多米诺场景概率;根据多米诺场景概率和人体脆弱性模型,计算目标点个人风险值;以LNG加注时火灾爆炸事故为例,计算个人风险值。通过案例分析,对比考虑多米诺效应和不考虑多米诺效应2种情况所得出的个人风险值。最终研究表明:考虑多米诺效应所得出的个人风险值明显高于不考虑多米诺效应所得出的值,且更加准确。

LNG池火热辐射模型及安全距离影响因素研究

重点对LNG池火热辐射模型,模型应用方式,以及热辐射安全距离的影响因素做了详细研究,给出池火热辐射模型采用及安全距离计算的方法。对常用的热辐射计算模型(点源模型、LNGFire3和PoFM ISE模型)加以介绍,并对3种模型做了对比研究。PoFM ISE模型充分考虑大池火直径时不完全燃烧的因素以及风速对火焰高度的影响,建议当风速大于1.5 m/s,池火直径大于20 m时采用。同时,进一步研究影响LNG池火热辐射安全距离的各种因素,包括池火直径、风速、环境温度和湿度,从而得出不同条件下池火热辐射安全距离的要求。

LNG加注趸船安全距离确定方法研究

为确定液化天然气（LNG）加注趸船与周边建（构）筑物的安全距离,对趸船LNG储罐和加液臂泄漏后果进行数值模拟计算。利用FLACS软件,计算不同泄漏场景LNG气云扩散距离;采用自主开发的LNG火灾计算软件LNGFHR＋计算趸船储罐泄漏和加液臂泄漏池火热辐射强度的影响距离。结果表明：LNG泄漏量、气象条件、风向等均会对LNG气云的扩散距离产生影响;储罐泄漏池火热辐射影响距离大于加液臂的影响距离。根据计算结果,确定LNG加注趸船与重要公共建筑物的安全距离为120-150 m,与民用建筑物的安全距离为85-110 m,与生产厂房、库房和甲、乙、丙类液体储罐的安全距离为90-110 m。

LNG罐车泄漏火灾罐体超压失效预警及防控

LNG作为清洁能源利用的重要组成部分,带来了大量道路罐车运输需求,并引发对其安全的关注。为此,以实际事故为背景,面向LNG罐车泄漏火灾罐体超压失效过程,特别针对事故凸显的泄漏—火灾—罐体超压循环激励特点,通过耦合罐车泄漏工艺流程和LNG火灾燃烧热模型,并基于压力容器破裂预测公式,建立了LNG罐车泄漏火灾超压失效预测模型及其求解方案,可快速计算罐体超压失效时间、罐内压力、泄漏强度等参数,模型计算结果与事故调查结果具有良好的一致性。研究结果表明:(1)气相泄漏火灾不应导致罐体超压失效;(2)液相泄漏火灾罐体充装率高,罐内压力攀升速度、峰值压力、泄漏速率都将增加,到达峰值压力的时间将降低,意味着更大事故风险。从泄漏火灾超压预警的角度,确定了不同充装率下液相泄漏罐体最危险泄漏孔径、最短预警时间和最大安全泄漏孔径,以及不会发生罐体超压失效的最大安全充装率。结合事故暴露和道路运输存在的问题,提出了罐体设计、道路驾驶和事故应急的注意事项,并推荐罐体不同充装率应对液相泄漏火灾所需的最小消防喷淋降温水量,以期为预防和控制事故LNG罐体超压失效提供支持。

液化天然气(LNG)码头消防系统设计

针对LNG码头消防系统设计中消防水炮是否要兼顾船舶的冷却消防,以及逃生通道冷却水喷雾系统和集液池如何设置等问题,结合相关的规范、文献和工程项目经验,分析码头的消防水炮要兼顾船舶冷却消防的必要性,并给出码头逃生通道冷却水雾设计范围的依据,明确水雾喷水强度的单位和取值,也列出集液池容积的计算方法,为更加合理地设计相应的消防系统提供参考,真正起到保护码头人员和财产安全的作用。

加注LNG燃料的船舶安全管理措施研究

为给液化天然气(LNG)动力船舶的安全管理体系建立提供参考,文章从LNG燃料加注5种模式比较及加注注意事项、LNG翻滚和间歇泉的原因及措施、LNG泄漏及火灾的对策等方面进行研究。结果表明:不同气源的LNG分开储存并采取合适的进料方式可预防LNG翻滚;需预置接液盘、水幕和护板等预防LNG泄漏,若泄漏发生,可视情采用贴堵法或塞堵法,同时配合使用水幕系统;LNG着火时,可综合运用水幕隔离、消防冷却、泡沫覆盖和干粉灭火。此外,向上实心锥形水幕控制LNG扩散效果最好,且水幕高度需高于云团2倍以上;高倍泡沫可明显降低LNG的挥发,但对最小有效淹没深度有要求;干粉降低池火最高温度明显,使用时需喷洒到火焰根部。

LNG双燃料远洋大型集装箱船消防灭火系统设计

相比柴油燃料,液化天然气(LNG)燃料具有高热值、低价格、低排放等优点,在船舶动力领域内的应用和广泛推广已经成为必然趋势。LNG常以低温状态储存,一旦泄露会迅速沸腾汽化,与空气混合形成爆炸性混合物,极其危险。为实现LNG动力船火灾风险的有效控制,以20 000箱LNG/柴油双燃料远洋大型集装箱船为研究对象,分析LNG燃料自加注至燃烧的使用过程,根据需求提出一套包含可燃气体探测、水喷淋、干粉灭火和燃气处理间灭火在内的完整消防灭火系统设计方案,并通过阐述各部分的设计依据、原理及功能作用说明了设计的有效性。