错流旋转填料床气相压降特性

旋转填料床的气相压降是旋转填料床应用和设计的一项重要指标。在气液两相错流流动条件下,利用空气-水系统对错流旋转填充床的气相压降进行分段模型化和实验研究。按照错流旋转填料床气体流动的路径将气相压降分为进口压降、填料层压降、集气段旋转动能转化压降和出气段压降。推导出压降与操作工况的关联式,其计算值与实测值吻合较好。实验表明错流旋转填料床的气相总压降与气体流量、旋转床转速、液体流量有关。在高转速和小气量的条件下,气相压降随气量增大先下降后上升;其他情况随气量增大而上升。错流旋转填料床气相压降随转速上升而下降,在小气量情况下转速对气相压降有明显影响。气相压降随进液量的增大而增大,当旋转填料床在低转速时进液量对气相压降有明显影响。     

网板填料复合旋转床的流体力学与传质性能

开发了一种新型的气液接触设备——网板填料复合旋转床。常压下以空气-水物系和乙醇-水物系在网板填料复合旋转床中进行流体力学与传质性能实验,考察了气液流量和转子转速对网板填料复合旋转床压降和传质性能的影响。实验结果表明,气体流量和转子转速的增大均使干、湿床气相压降增大;液体流量的增加对湿床压降的影响不明显。回流量和转速的增加均使等板高度减少至一定值后几乎不变。网板填料复合旋转床具有通量大、效率高、压降小的特点。     

三种填料结构旋转床传质及压降性能对比

为了考察自主设计的新型板式旋转填料床传质及压降性能,分别以NaOH-H_2O和空气-水为实验体系,采用对比实验的研究方法,考察了转速、液量和气量对新型板式填料床、传统丝网填料床和鲍尔环填料床的传质与压降性能的影响。传质性能研究表明:在相同操作条件下,丝网填料床传质性能最优,但新型板式填料床传质性能与丝网填料床相差不大(<1.0 s~(-1));压降性能研究发现,气量是影响填料床压降的重要因素,且在相同操作条件下,压降值始终有丝网填料床>鲍尔环填料床>新型板式填料床,丝网填料床压降值与新型板式填料床相差33%以上。新型板式填料床在传质效率损失不大的情况下,损失了较低能耗,表现出优良的综合性能。     

三角形螺旋填料旋转床气相压降特性

为深入了解三角形螺旋填料旋转床气相压降的影响因素及规律,以空气-水为实验物系进行了实验和模型研究。改变气、液流量及转速测定气相压降的实验结果表明,气体流量和转速的增大均使干、湿床气相压降增大;液体流量增大时湿床气相压降先减小,而后基本保持不变;该旋转填料床具有气相压降小、操作弹性大的优点。按照气相压降产生的机理,将其分为局部压降、离心压降、转子外内腔压降和填料主体压降4部分进行模型研究,其中用旋涡理论描述转子外内腔压降、用简化的模型描述填料主体压降是新提出的方法,且所建模型能较好地描述气相压降的规律。     

低阻高效同心环碟片填料旋转床流阻和传质特性研究

采用新型旋转床填料———同心环波纹碟片填料 ,对三种填料间距结构 ,在干、湿床两种状态下的气相压降随碟片填料间距、转速、气液流量的变化关系进行了试验研究 ,与有关文献的多孔介质填料压降结果对比 ,在相近的操作条件下 ,同心环波纹碟片填料的阻力分别是其阻力的 2 0 % (干床 )与 40 % (湿床 ) ,同心环波纹碟片填料的体积传质系数是它们的 1 9～ 2 5倍。     

并流旋转床压降与传质特性的研究

利用水-空气系统对并流旋转床的气相压降进行了研究,并与逆流旋转床气相压降进行了对比。研究结果表明：并流较逆流旋转床的气相压降低;并流旋转床的气相压降随气体流量的增大而增大,随液体流量的增大而减小,随转速的增大明显降低;而逆流旋转床的气相压降随转速的增大明显升高。利用水吸收SO2的实验对并流旋转床的传质特性进行了研究。研究结果表明：并流旋转床填料层内各点的体积传质系数随着气体流量、液体流量和转速的增大而增大;填料层半径由70mm增大至90mm时,并流旋转床的体积传质系数迅速增大,而后并流旋转床的体积传质系数随半径的增大而减小。对并流和逆流旋转床填料层内体积传质系数进行了对比。结果表明：填料层半径由70mm增大至130mm时,并流旋转床的体积传质系数较逆流时大;当半径大于130mm后,逆流旋转床的体积传质系数大于并流旋转床的体积传质系数,且随半径增大而增大。根据研究结果,提出了降低系统压降的设想,即并流与逆流旋转床串联操作。     

不同填料错流旋转填料床气液传质特性研究

为了探索不同填料错流旋转填料床的传质性能,以Na2CO3水溶液吸收空气中硫化氢为实验体系,对装有不锈钢丝网、塑料波纹孔板和θ环填料的错流旋转填料床的气液传质性能进行研究。实验确定的适宜操作条件为:超重力因子7.8,气体流量2 m3/h,液气比20 L/m3,碳酸钠质量浓度12 g/L;在此条件下,3种填料的脱硫率均可达到90%以上。在相同操作条件下,不锈钢丝网填料的脱硫率及气相总体积传质系数大于塑料孔板填料大于θ环填料;错流旋转填料床中,规整填料的气液传质效果优于乱堆填料。文中的研究结果为错流旋转填料床填料的选取及在脱硫方面的应用提供了依据。     

错流旋转填料床气相压降特性研究

旋转床的气相压降是旋转床工程设计的一项重要指标。笔者利用空气,水系统对错流旋转填料床的气相压降进行实验研究。结果表明：在实验范围内,错流旋转床压降是逆流旋转床的十分之一;对错流旋转床压降影响较大的是转速和气量,与液流量几乎无关。     

新型填料结构旋转床传质特性

以CO2-NaOH溶液为工作介质,研究了填料特性、超重力因子、气体流量和液体流量等对不同填料结构旋转床传质特性的影响.结果表明:体积传质系数随液体流量、超重力因子和气体流量的增加而增大;对比六种填料结构的综合性能,不锈钢多孔波纹板和塑料多孔板填料结构较优;在相近的操作条件下,不锈钢多孔波纹板的体积传质系数比文献丝网错流旋转床高0.95～2.10倍、与逆流旋转床相当,比传统气液传质设备高1～2个数量级.对实验数据进行回归分析得出了体积传质系数的关联式,其平均误差小于10%.     

不同规整填料旋转床的传质性能对比

采用Na₂CO₃-H₂S为体系,利用规整丝网填料和新型塑料填料的错流旋转床为吸收设备,探究了两种填料床的传质性能,通过理论推导气液传质系数K_y和K_ya的表达式,考察了液量、气液比、超重力因子对脱硫率、K_y和K_ya的影响。实验结果表明:在相同条件下,规整丝网填料床的脱硫率略高于新型塑料填料床,约为3%～4%,但K_y、K_ya和压降分别是新型塑料填料床的0.25～0.5、0.8～0.9和0.3～0.5倍。通过文献对比分析,在相近工况条件下,新型塑料填料床的K_ya比散装丝网填料床提高了1.45倍。并对实验数据进行回归,拟合出K_y、K_ya与气相雷诺数Re_G、液相韦伯数We_L和伽利略数Ga之间的关联式。     

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。