超临界沥青喷雾造粒中的戊烷闪蒸CFD模拟

重油梯级分离技术作为重油轻质化的新工艺,它通过耦合渣油萃取和沥青喷雾造粒过程,有效的简化重油处理的工艺流程,减少设备成本。在此工艺流程中,处于超临界状态的戊烷的闪蒸速率对沥青造粒质量起到了关键作用。根据其减压过程中的质量和热量传递机理,改进了戊烷闪蒸的经验模型,并将其植入到CFD软件FLUENT中,使其能较为准确的预测闪蒸雾化的非平衡热力学过程。同时对气液戊烷和沥青的三相闪蒸流动过程进行了数值模拟,结果显示喷嘴结构是控制闪蒸速率的关键,直接影响了沥青造粒的质量;此外沥青相的加入为戊烷的相变过程提供了更多能量,提高了戊烷在喷嘴内的汽化率。     

新型喷嘴R404a闪蒸瞬态喷雾冷却传热特性

制冷剂闪蒸瞬态喷雾冷却在激光治疗血管性皮肤病手术中得到广泛应用, 主要用于激光照射前选择性地冷却表皮。本文搭建了喷雾冷却实验台, 设计不同长径比膨胀腔新型透明喷嘴, 应用薄膜热电偶瞬态温度快速测量技术和杜哈梅尔定理计算方法对比分析了膨胀型喷嘴和传统直管型喷嘴应用低沸点的新型制冷剂R404a的闪蒸瞬态喷雾冷却表面动态传热特性。应用高速摄像仪和采用背光法对新型喷嘴膨胀腔内部制冷剂流动形态进行观察, 发现制冷剂液体在膨胀腔内首先发生一次闪蒸破碎, 剧烈相变产生大量气泡, 可导致液滴温度在喷嘴内部大幅降低, 而直管型喷嘴制冷剂只在喷嘴喷出后才形成闪蒸喷雾并降温。因此, 膨胀腔型喷嘴比直管喷嘴具有更佳的冷却效果, 能够产生更低的冷却温度, 更高的热通量、传热系数和换热量。膨胀腔长径比是影响此类喷嘴喷雾冷却效果的关键因素, 在长径比1:2时其冷却能力最强、有效冷却时间最长。     

跨临界CO2快速膨胀过程中非平衡冷凝和闪蒸机理的数值研究

跨临界CO₂在高速膨胀时,压力和温度剧烈下降,会发生非平衡相变。其中在天然气超声速分离设备和超临界CO₂离心压缩机中CO₂会发生非平衡冷凝相变;在引射膨胀制冷系统中,跨临界CO₂在引射器主动喷嘴中发生非平衡闪蒸相变。为解决跨临界CO₂在膨胀过程中物性变化剧烈,非平衡相变模拟困难的问题,构建了新型非平衡相变CFD模型,以研究跨临界CO₂在超声速缩放喷嘴中的非平衡冷凝和非平衡闪蒸的相变过程和膨胀机理,模型耦合了温度驱动的蒸发-冷凝相变机制和压力驱动的空化-冷凝相变机制,并用文献中的试验结果验证了模型的准确性。研究结果表明,在冷凝相变过程中,由压力驱动的冷凝传质具有主要影响,压力驱动的冷凝传质主要存在于喷嘴喉部与内流区域,温度驱动的冷凝传质主要存在于喷嘴渐扩段壁面。冷凝传质速率随着进口压力的增加和进口温度的降低而增加,从而使冷凝的非平衡程度和喷嘴内的干度降低,喷嘴渐扩段内达到声速的位置也相应延后。在闪蒸相变过程中,由温度驱动的蒸发传质占据主导,蒸发相变主要发生在喷嘴喉部附近,空化相变主要发生在喷嘴渐扩段,两相CO₂在喷嘴的渐扩段达到声速。随着喷嘴进口压力的增加和进口温度的降低,闪蒸的非平衡程度增加,使喷嘴内的干度减小。本研究有助于厘清跨临界CO₂快速膨胀中的非平衡闪蒸和冷凝相变机理,并为跨临界CO₂膨胀设备的分析和优化设计提供参考。     

跨临界CO2快速膨胀过程中非平衡冷凝和闪蒸机理的数值研究

跨临界CO₂在高速膨胀时,压力和温度剧烈下降,会发生非平衡相变。其中在天然气超声速分离设备和超临界CO₂离心压缩机中CO₂会发生非平衡冷凝相变;在引射膨胀制冷系统中,跨临界CO₂在引射器主动喷嘴中发生非平衡闪蒸相变。为解决跨临界CO₂在膨胀过程中物性变化剧烈,非平衡相变模拟困难的问题,构建了新型非平衡相变CFD模型,以研究跨临界CO₂在超声速缩放喷嘴中的非平衡冷凝和非平衡闪蒸的相变过程和膨胀机理,模型耦合了温度驱动的蒸发-冷凝相变机制和压力驱动的空化-冷凝相变机制,并用文献中的试验结果验证了模型的准确性。研究结果表明,在冷凝相变过程中,由压力驱动的冷凝传质具有主要影响,压力驱动的冷凝传质主要存在于喷嘴喉部与内流区域,温度驱动的冷凝传质主要存在于喷嘴渐扩段壁面。冷凝传质速率随着进口压力的增加和进口温度的降低而增加,从而使冷凝的非平衡程度和喷嘴内的干度降低,喷嘴渐扩段内达到声速的位置也相应延后。在闪蒸相变过程中,由温度驱动的蒸发传质占据主导,蒸发相变主要发生在喷嘴喉部附近,空化相变主要发生在喷嘴渐扩段,两相CO₂在喷嘴的渐扩段达到声速。随着喷嘴进口压力的增加和进口温度的降低,闪蒸的非平衡程度增加,使喷嘴内的干度减小。本研究有助于厘清跨临界CO₂快速膨胀中的非平衡闪蒸和冷凝相变机理,并为跨临界CO₂膨胀设备的分析和优化设计提供参考。     

注射过程喷嘴内物料温度和压力的模拟与分析

利用Fluent软件对注射过程中物料在喷嘴内的流动进行了模拟,分析了喷嘴内剪切热产生的位置及喷嘴尺寸与物料温度变化和压力降的关系。结果表明,注射过程中喷嘴内最高温升位置出现在壁面附近的很小区域内,温升变化率随喷嘴圆管直径的增加而降低,随喷嘴圆管长度的增加而提高;喷嘴出口处物料温度随喷嘴圆管直径增加逐渐趋向均匀;注射过程中喷嘴内压力降随喷嘴圆管直径减少和长度的增加而提高。     

高温高压喷雾闪蒸的蒸发特性

基于新型高温高压喷雾闪蒸实验台,以水为工质,研究初始条件和运行条件对闪蒸蒸发特性的影响。首次将液体初始温度提高至100℃以上,将闪蒸罐运行压力保持为正压,并使用具有独特双S形叶片的涡旋实心锥喷嘴,将液体向上或向下喷入闪蒸罐。实验过程中液体初始温度为135～150℃,闪蒸压力分别为121、126、131、136、141、146 kPa,液体过热度为30～46℃。实验结果表明,闪蒸蒸汽流量随初始温度的提高而增大,随闪蒸压力的提高而减小。液体向下喷射比向上喷射产汽量更高,蒸汽带水更少。闪蒸效率随过热度呈线性增长,在大量实验数据基础上拟合出二者之间的经验公式。实验结果为高温高压喷雾闪蒸的工业应用提供借鉴。     

80万t/a丙烷脱沥青装置沥青闪蒸塔优化设计

针对某石化公司80万t/a丙烷脱沥青装置沥青闪蒸罐D-107进行优化设计,从而达到减少沥青携带的作用。对沥青闪蒸罐D-107进行分析,发现沥青闪蒸罐发生携带的根本原因在于两相分离不充分,因此增加两相的分离时间即可达到充分分离的效果。经检查设计和基本操作参数,该闪蒸罐最优停留时间为15min,由设计方案优化可知:增加原有闪蒸罐高度及重新设计闪蒸罐均可将停留时间增加至15min,从而达到充分分离的效果。而重新设计沥青闪蒸罐D-107/A,可在装置停工时安装已建好的新沥青闪蒸罐,不影响装置正常开工运行,而且罐体高度适中。本文推荐后者。     

RESS法制备微细颗粒的喷嘴内流动特性的数值模拟

为了对RESS法制备微细颗粒过程中喷嘴内流体规律进行研究,通过对超临界流体快速膨胀法（rapid expansion of supercritical solution,RESS）流动过程的研究与分析,建立了喷嘴内超临界流体流动数学模型。对喷嘴内流场和温度场进行研究,考察了预膨胀压力、预膨胀温度、长径比等操作参数对RESS过程的影响,模拟结果表明,喷嘴内部的密度曲线在喷嘴入口段,几乎没有发生变化,而在直管段和出口膨胀段超临界流体密度发生急剧下降;随着长径比的增大,喷嘴内密度曲线变陡;随着长径比的增大,喷嘴出口处流体的温度都变小,过饱和度变大,结晶颗粒使得更为细小。该模型和模拟过程能够为实现制备均一微细颗粒的实际操作条件和优化过程参数奠定基础。     

高温高压喷雾闪蒸的蒸发特性

基于新型高温高压喷雾闪蒸实验台,以水为工质,研究初始条件和运行条件对闪蒸蒸发特性的影响。首次将液体初始温度提高至100℃以上,将闪蒸罐运行压力保持为正压,并使用具有独特双S形叶片的涡旋实心锥喷嘴,将液体向上或向下喷入闪蒸罐。实验过程中液体初始温度为135~150℃,闪蒸压力分别为121、126、131、136、141、146 k Pa,液体过热度为30~46℃。实验结果表明,闪蒸蒸汽流量随初始温度的提高而增大,随闪蒸压力的提高而减小。液体向下喷射比向上喷射产汽量更高,蒸汽带水更少。闪蒸效率随过热度呈线性增长,在大量实验数据基础上拟合出二者之间的经验公式。实验结果为高温高压喷雾闪蒸的工业应用提供借鉴。     

双层喷嘴进料提升管内气固流动混合特性的大型冷模实验研究

为改善催化裂化工艺的产品分布,在传统单层向上原料喷嘴进料结构基础上,增加了2个对称、向下的“副喷嘴”。通过一套大型冷模实验装置,考察这种新型双层喷嘴进料段结构内气固流动混合特性,同时利用射流“二次流”理论,分析了逆向喷嘴射流二次流在提升管内的形成发展过程。实验结果表明,与传统单层向上喷嘴（主喷嘴）结构相比,双层喷嘴结构能够改善主喷嘴附近油剂匹配程度,提高气固接触效率。同时副喷嘴的加入可以将提升管进料段长度缩短1/3,减少油剂混合时间,加快气固相达到均匀稳定,实现抑制油气过度裂解,提高目标产品收率,降低生焦量的目的。     

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。