紧急关断阀关断延迟对天然气管道泄漏过程的影响

准确判断泄漏速率对控制泄漏和计算应急区域范围非常关键,但现有天然气管道泄漏速率计算多在稳态的持续泄漏或紧急关断（ESD）阀同时关闭的动态泄漏假设下得到结果,与实际存在差别。本文结合管道过程,构建基于HYSYS的天然气集输管道泄漏等效模型,就ESD阀关断顺序和延迟对管道流量和泄漏速率的影响进行了模拟分析。结果表明,随着泄漏孔径的增加,管道内将出现逆流现象,管道ESD阀关断延迟顺序对小孔泄漏和大孔泄漏速率的控制存在明显不同的影响,对释放持续时间的影响较小。     

尿素合成塔液相泄漏蒸气爆炸压力计算

基于热力学理论,对尿素合成塔液相区泄漏的蒸气爆炸进行了理论计算。将裂纹型缺陷作为泄漏口,并且认为裂纹张开面积随内部压力载荷的变化而变化,从而对泄漏速率产生影响,进而影响内部爆炸压力载荷的反弹。计算结果表明:盛装高温、高压物料的尿素合成塔的液相区泄漏能够引发蒸气爆炸。     

油气管道腐蚀安全评价方法的对比

为了避免石油和天然气输送管道的腐蚀损坏,对比研究传统的ASME B31G规范、修正的ASME B31G规范、PCORRC方法、DNV RP-F101规范和AGA NG-18方法5种油气管道腐蚀安全评价方法,考察流变应力和膨胀系数对油气管道安全评价的影响,利用这5种油气管道安全评价方法对不同强度等级油气管道进行剩余强度的计算,并与爆破压力进行对比,分析其保守性和准确性。结果表明:随着管线钢级数的不断提高,用不同方法计算出的流变应力之间的差值不断减小;对于短腐蚀缺陷,膨胀系数对安全评价结果影响较小,对于长腐蚀缺陷,修正的ASME B31G规范和DNV RP-F101规范对剩余强度的评估更合理准确;传统的ASME B31G规范计算结果最为保守;修正的ASME B31G规范保守性大大改善,而且准确性高,稳定性好,特别适合于低中强度油气管道的安全评定;PCORRC方法和DNV RP-F101规范不适合进行低强度钢和高强度钢的安全评定;AGA NG-18方法适用于高强度钢的安全评定。所得结论对于油气管道腐蚀安全评价有着重要的参考意义。     

含腐蚀缺陷长输管道剩余强度影响参数定量评价

针对管道运行过程中腐蚀缺陷导致管道事故频繁发生等问题,主要采取了NG-18、ASME B31G-1991、API 579和DNV RP-F101等方法对管道剩余强度的评价。四种评价方法对指标参数失效压力、流变压力、缺陷长度、Folias鼓胀因子以及腐蚀缺陷面积计算各有不同,分别做了各参数与评价结果定量影响研究。实验研究表明:管线钢材级别越高,不同定义下计算的流变压力相差减小,对管道剩余强度评价的影响较小;随着缺陷长度的增加,鼓胀因子相对差逐渐变大,对管道剩余强度评价的影响较为敏感。对于短缺陷管道,NG-18评价方法较为合适;基于实际爆破数据,相对于ASME B31G-1991评价方法,DNV RP-F101评价结果误差较小;对腐蚀缺陷管道缺陷面积的计算,ASME B31G-1991方法精度较高,是一种普遍适用的评价方法。     

天然气管道泄漏过程的参数变化研究

城市天然气管道泄漏是个复杂的非稳态过程,整个泄漏过程中气体流动状态随时间发生变化,利用计算机计算泄漏质量流量、泄漏速度等参数的变化。把泄漏过程分成多个时间段进行计算,单个时间段的计算是稳态泄漏,再结合理想气体状态方程、绝热方程、伯努利方程和质量守恒定律进行计算,然后把计算数据进行拟合得出泄漏质量流量、管道内压力、泄漏气体质量以及泄漏速度随时间的变化规律,为提高泄漏扩散模拟评价结果的准确性提供保证。     

天然气管道泄漏速率的确定

天然气泄漏速率是模拟评价天然气管线泄漏事故过程中的重要因素之一,对其研究将有利于提高模拟评价结果的正确性。应用热力学和气体动力学理论,结合理想气体状态方程、绝热方程和能量守恒方程,研究分析了天然气管道的泄漏过程,分别给出了在临界泄漏阶段以及亚临界泄漏阶段的泄漏速率计算公式,为天然气管输安全工程的相关计算提供了可靠的理论依据。     

瞬变流能量损耗对管道泄漏检测的影响

管道泄漏检测是管道安全管理的重要方面,基于实时仿真的泄漏检测方法是管道泄漏检测的技术路线之一。传统的瞬变流模型采用拟定常假设,对管道内的能量衰减描述不够准确,易导致模型的预测值和测量值出现较大偏差。本文在总结管道模型进展基础上,研究瞬变流能量损耗对仿真的影响和基于瞬变流模型的泄漏检测方法。结果表明,采用瞬变切应力模型能够更准确地描述管道内的能量衰减,更好地实现基于模型的泄漏检测。     

城市输送管道小泄漏特征及规律分析

利用实验室油气管道平台和声发射仪,建立了模拟城市输送管道泄漏检测系统。通过实验对气、液管道小泄漏信号特征与衰减特性进行了分析,在改变管道压力、泄漏量以及传感器间距等参数状态下,分别分析了管道泄漏信号的幅值随管道压力、泄漏量、传感器间距变化的规律,对城市输送管道泄漏检测进行了有益的探索。     

固定式海洋石油平台管道应力分析方法

文章依据标准规范和相关书籍文献,结合多年来固定式海洋石油平台项目的管道应力分析经验,总结了海洋石油平台管道的应力分析方法、要求及特点。海洋石油平台的应力分析主要依据ASME B31.3规范,ASME B31.4/B31.8规范第八章,以及DNV-RP-D101推荐做法。分析方法涉及静态分析、动态分析和疲劳分析等三个方面。主要分析管道包括油气系统管道、高温热油管道、低温放空管道、大型泵和压缩机连接管道、火炬臂管道、消防管道、栈桥管道和海洋立管管道等关键管道系统。分析内容主要包含管道应力、管道位移、法兰泄漏校核、支架载荷、设备管嘴载荷和管系模态自然频率等。     

气相乙烷管道泄漏扩散特征模拟分析

为研究气相乙烷管道泄漏扩散后的影响,以某公司拟建的一条乙烷输送管道为工程背景,采用CFD(计算流体动力学)软件,对不同泄漏孔径、不同风速下的气相乙烷管道泄漏进行了模拟分析,探讨其泄漏扩散特征以及危险范围的演变情况。结果表明：随泄漏孔径增大,乙烷的扩散形状发生改变,小孔泄漏扩散在土壤中的形状演变特征分为前、中、后期3个阶段,而管道全尺寸泄漏在大气中的扩散分为无风时的垂直射流扩散以及有风时的横向扩散;随泄漏孔径的增大,乙烷泄漏扩散范围变大,危险区域变大;随风速增大,乙烷全尺寸泄漏扩散高度降低,且危险浓度最远扩散距离达到峰值的时间缩短。     

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.     

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.     

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。