蒸发系统传热温差的计算及减小温差损失的途径

本文介绍了蒸发系统传热有效温差的计算方法。着重对影响静压所致沸点升高的各种因素进行了分析,从蒸发器的选型和结构设计等方面指出减小静压温差损失的途径。最后对有效温差如何合理地分配于各效蒸发器的问题进行了讨论。蒸发系统的传热总温差△T等于第一效加热蒸汽的饱和温度T_S与末效冷凝器的蒸汽饱和温度t_C之差,即△T=T_S-t_C 由此可见,生蒸汽压力和冷凝器可能达到的真空度这两个因素决定了系统传热总温差,而后者取决于冷凝器的冷却水温度及真空设备性能。但分配到各效蒸发器的传热有效温差还要扣除如下三项温差损失: (1)溶液的沸点升高; (2)液柱静压头和流动摩擦压降所致的沸点升高; (3)效间二次蒸汽管路压降所致温差损失。下面通过对各项温差损失的计算及分析,指出在蒸发系统的设计中减少温差损失的途径,从而提高蒸发装置的生产能力。     

碳酸钾生产中除氨新工艺实验研究

现有碳酸钾生产工艺中采用蒸发除氨,由于除氨不彻底,导致蒸发二次蒸汽中含有大量氨气和二氧化碳,使蒸发器的传热系数大大降低,从而增加了蒸发能耗;另一方面,挥发出的氨气和二氧化碳又难以集中回收,造成资源浪费,且增加原料成本费用。采用解吸法除氨,对料液温度、气液比、喷淋密度、气提时间、初始浓度等因素进行研究。实验结果表明,对于定量的处理料液,料液温度、气液比、喷淋密度、气提时间对碳酸氢铵分解影响较大,初始浓度对其影响较小。最佳工艺参数：料液温度为85 ℃、气液体积比为30∶1、喷淋密度为55 m³/（m²·h）,汽提时间为2.5 h,此时除氨率为95.48%。     

大型低温多效蒸发海水淡化装置传热过程热力损失分析

基于低温多效蒸发海水淡化装置的各种阻力和海水沸点升高(BPE)关联式,计算了海水淡化装置中流动阻力、海水沸点升高等造成的传热过程热力损失,分析了各项热力损失在各效蒸发/冷凝器中的分布、随蒸发/冷凝器数量的变化规律等。结果表明:产水量、浓缩比和加热蒸汽温度等参数均保持不变的前提下,总的热力损失随着装置的蒸发/冷凝器数量而增加;BPE引起的热力损失占最大比例,但流动阻力引起的热力损失不可忽略。通过对海水淡化装置热力损失的分析,提出了低温多效蒸发海水淡化装置"小温差、低流阻、饱和态、高敏感"的工作特征理论。     

吸收膜蒸馏淡化海水研究

针对吸收膜蒸馏(OD)系统的进料液和吸收液的温度非常接近甚至相同,其传质过程无相变热损失,有可能实现能耗较低的膜蒸馏过程这一设想,尝试开展OD法海水淡化研究。以葡萄糖水溶液为吸收液,考察了温度、料液及吸收液流速、吸收液含量等参数对OD过程的影响。结果表明,随温度的升高,膜通量增大明显;随吸收液和料液流速的增大,膜通量增大,且料液浓缩倍数较小、含量较低时,吸收液流速相对料液流速,对通量的影响更大,反之,料液浓缩倍数较大、含量较高时,料液流速的影响更大;随着吸收液含量的增大,膜通量也相应增大。试验过程中未发生疏水膜的亲水化渗漏现象。     

大型低温多效蒸发海水淡化装置传热过程热力损失分析

基于低温多效蒸发海水淡化装置的各种阻力和海水沸点升高（BPE） 关联式,计算了海水淡化装置中流动阻力、海水沸点升高等造成的传热过程热力损失,分析了各项热力损失在各效蒸发/冷凝器中的分布、随蒸发/冷凝器数量的变化规律等。结果表明：产水量、浓缩比和加热蒸汽温度等参数均保持不变的前提下,总的热力损失随着装置的蒸发/冷凝器数量而增加;BPE引起的热力损失占最大比例,但流动阻力引起的热力损失不可忽略。通过对海水淡化装置热力损失的分析,提出了低温多效蒸发海水淡化装置“小温差、低流阻、饱和态、高敏感”的工作特征理论。     

纳滤膜处理含镍电镀废水的中试研究

采用纳滤膜法对电镀镍漂洗废水及金属镍的在线回用进行中试研究,维持p H、TDS、电导率、温度等条件不变,改变操作条件,研究了操作压力、进水流量、料液浓度、运行时间、产水比对膜分离性能的影响。研究结果表明,增加操作压力、进水流量、料液浓度都可提高Ni2+截留率及浓缩倍数;保持各影响因素恒定运行时,纳滤膜对Ni2+截留率及浓缩倍数随运行时间的延长逐渐增大,稳定运行40 h后接近最大截留率及最大浓缩倍数,截留率达75%左右,浓缩倍数在6.2倍左右;产水比对Ni2+截留率有较大影响,产水比为1∶1、进水流量为6 t/h时,Ni2+截留率为65.7%,浓缩倍数为2.4倍。     

低压蒸汽环境中水蒸发界面温度和蒸发速率的实验研究

蒸发相变广泛存在于薄膜过程及晶体生长等工业生产和日常生活中,液层表面蒸发和热毛细对流相互影响、相互制约,使得蒸发界面能量传递机制变得非常复杂。为了深入了解水在低压纯蒸汽环境中的蒸发特性,对环形液池内水蒸发时的温度分布和蒸发速率进行了一系列实验研究。环形液池壁温控制在3～15℃之间,蒸发环境压力在394～1467 Pa之间变化,开始测量时液层深度为10 mm。结果表明,蒸发界面气相侧温度总是高于液相侧,气液界面存在明显的温度跳跃。随着压比减小,蒸发速率增加,界面温度跳跃随之增大;随着距壁面距离增加,局部蒸发速率降低,温度跳跃值减小;相同压比下,随着壁面温度的升高,气相侧热通量减小,蒸发界面温度跳跃值整体降低;在实验范围内测得的最大温度跳跃值为2.56℃。由于蒸发冷却效应和热毛细对流的耦合作用,蒸发界面下液相侧存在一个厚度为2 mm左右的温度均匀层,且壁面附近温度均匀层厚度大于中间区域厚度。在温度均匀层内,径向温度梯度诱导的热毛细对流将热量从壁面传输至气液界面以补偿蒸发所需汽化潜热;在温度均匀层以下,浮力对流和导热共同作用使得液相温度迅速升高。     

薄膜蒸发器传热蒸发性能的实验研究

在自行研制的0.4m2薄膜蒸发器实验测试装置基础上,对介质水及烧碱溶液进行了蒸发实验,得到了在不同工艺操作参数下薄膜蒸发器内各料液总传热系数K和蒸发强度EI的变化曲线。实验结果表明,转子转速及进料量对设备总传热系数K及蒸发强度EI影响显著,各料液均存在最佳进料量。粘度增加,总传热系数K相应减少,蒸发强度EI相应增加,实验与数值模拟结果变化规律一致。研究结果表明,从蒸发强度而言,薄膜蒸发器更适合于高粘度料液的蒸发浓缩。     

接触式蒸发处理垃圾渗滤液膜浓缩液试验研究

采用接触式蒸发处理垃圾渗滤液纳滤膜浓缩液,考察了气体温度、气体流量、初始pH和蒸发率对冷凝液水质的影响。结果表明:随着气体温度的增加,稳定蒸发温度不断提高,冷凝液COD先降低后升高,而NH_3-N先升高后降低;随着气体流量的增加,冷凝液COD先降低后升高,而NH_3-N不断增加;随着初始pH的升高,冷凝液COD降低,而NH_3-N则相反。蒸发初期,冷凝液COD及NH_3-N较高,随蒸发率的提高,其含量不断降低,并在末期有所提高;蒸发初期和末期气体夹带较为显著。     

微乳液膜法萃取钕

进行了微乳液膜法萃取Nd3+的研究,考察了不同盐酸浓度时微乳液的溶水量及其对Nd3+的萃取率、内相富集浓度的影响,同时还考察了温度、料液浓度、缓冲剂对萃取Nd3+的影响.结果表明,随着盐酸浓度增大,微乳液溶水量增加;内相Nd3+富集倍数最高为24.3倍,料液Nd3+浓度相同时,内相Nd3+富集浓度和富集倍数随溶水量增加而减小,萃取率则变化不大,一般在70%～80%范围,于料液中加入缓冲剂对Nd3+的萃取率有很大影响.根据微乳液膜渗透速率方程计算了传质系数.通过在微乳液和料液之间加载一层亲水性微孔滤膜,避免了微乳液与料液直接接触所产生的乳化,内相泄漏也得到了抑制.     

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。