浅谈LNG接收站储罐压力控制方式

介绍LNG接收站BOG产生原因并运用不同方法计算出各种原因下的BOG产量,以此为基础探讨LNG接收站储罐压力控制的各种方式。通过对比BOG压缩外输、BOG再冷凝外输和BOG通过火炬、安全阀放空几种控制方式的能耗,结合现阶段接收站运行的实际工况,分析出使用BOG再冷凝低压外输工艺为目前工况下的最佳控制方式。     

LNG接收站火炬管网系统设计比较

火炬管网系统是LNG接收站中最重要的组成部分之一,同时也与BOG系统紧密相联,互相影响。针对国内现有LNG接收站主要的两种火炬管网系统进行比较,分析各自的优缺点,为其他项目的设计提供一定的参考意义。     

火炬管网设计及校核

本文对某LNG接收站火炬处理能力进行计算，确定最大火炬泄放量及对应工况。针对不同工况，利用Aspen Flare System Analyzer软件，根据实际火炬管线配管，建立模型，对火炬管网进行核算。最终确定此LNG接收站需新增一座处理能力为80 t/h的地面火炬，可以满足工艺设计要求。另外本文可为其他火炬管网的设计提供一定参考。     

基于FLARESIM模拟的LNG接收站高架火炬设计选型研究

火炬系统是维护LNG接收站安全运行的重要设备。为了直观有效的掌握高架火炬热辐射对接收站内设施及周边环境的影响，评估火炬设置的合理性与安全性。在相关规范内容的基础上细化LNG接收站火炬系统处理能力的选型工况，其作为重要的输入条件，提高火炬设计规模及火炬系统设计的准确性，在此基础上进一步通过FLARESIM软件对高架火炬包括筒体尺寸、火炬头及火炬高度等进行模拟计算，在标准允许范围内有效识别并评估热辐射对接受点的影响，以确定高架火炬的设计参数及布置位置。一般说来，常规LNG接收站火炬泄放量最大组合工况为储罐漏热+大气压降低+控制阀失效或储罐漏热+大气压降低+卸船充装时的置换和闪蒸，并通过调整火炬位置及火炬筒高度可以满足热辐射的要求及气体扩散浓度要求。     

LNG接收站中再冷凝工艺的技术分析及优化

LNG接收站在运行过程中会产生蒸发气(BOG),若不及时处理会造成接收站超压,而不得不放空至火炬燃烧,既浪费能源又污染环境。对于接收站正常操作工况下产生的BOG,通常采用再冷凝的工艺进行处理。介绍了国内对于BOG再冷凝工艺存在的2种设计理念,分析了固定LNG/BOG流量比例的设计模式存在的问题,对于设计理念中不完善部分进行了讨论;同时结合现场实际操作中出现的问题,验证该设计会导致再冷凝器中的液位出现较大波动,影响再冷凝器和整个接收站的稳定运行。对上述设计模式进行了优化,通过改变LNG与BOG流量比值,使再冷凝器内LNG为饱和状态,保证了再冷凝器的稳定运行。     

高压压缩机填料密封失效的原因分析

大型LNG接收站在运行期间会产生大量BOG,在外输量较小时,利用高压压缩机对BOG进行回收能够有效避免BOG直接排放火炬造成的经济损失和环境污染。首先介绍了高压压缩机在LNG接收站的应用以及某LNG接收站因高压压缩机运行而引起火炬燃烧的问题,再结合生产实际情况,对该问题进行深入分析和探讨,最终找到了问题的源头。     

LNG接收站增压-冷凝系统优化分析

增压-冷凝系统是LNG接收站的控制核心。介绍了增压-冷凝系统工艺流程,结合某LNG接收站运行过程中高压输送泵入口过滤器阻塞的情况分析了高压输送泵入口压力与过滤器压差间的变化规律以及在此情况下泵井放空管线配管对再冷凝器平稳运行的影响,对存在的问题提出了优化方案,从而保证增压-冷凝系统稳定运行。     

LNG接收站火炬系统设计应注意的问题

针对LNG接收站火炬系统设计中应考虑的主要因素,重点阐述了火炬设计能力的确定以及设计中如何保证排放物完全燃烧,防止下"火雨"和火炬系统的回火等问题.     

离心式BOG压缩机在LNG接收站中的应用分析

LNG接收站在运行过程中会产生BOG(boil-off gas,蒸发气),如果不及时处理会造成接收站超压,而不得不放空至火炬燃烧,既浪费能源又污染环境。目前,对于接收站正常操作工况,BOG通常采用再冷凝的工艺进行处理。其中,BOG压缩机是再冷凝处理工艺中的重要设备之一,通常选用往复式压缩机用于增压、输送BOG至再冷凝器。而随着接收站规模大型化,BOG产生量会大幅增加,受限于往复式压缩机的单台处理能力,需要设置多台压缩机,给运行、检维修等带来了更多的困难与不确定性。基于此,本文对离心式压缩机用于接收站中的BOG处理可行性进行研究与分析,为其它潜在应用的接收站提供一定的参考与借鉴。     

LNG接收站蒸发气(BOG)的产生和计算

液化天然气(LNG)接收站是储存、气化、外输LNG的场站,具有国家能源战略储备的功能,目前在国内发展迅速。由于LNG是低温流体,在接收站中其温度一般为-162～-150℃。分析BOG的生成机理,研究LNG接收站BOG的单元计算方法,在LNG接收站设计中占有重要的地位。BOG计算量过大,会导致BOG处理系统设计能力过量,增大建设成本;BOG计算量过小,BOG处理系统设计能力不足,导致站内BOG的大量放空,不仅浪费能源产生较大的经济损失,而且还污染环境。     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料，介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比，介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序，对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.