用空气模拟蒸汽的烘缸汽刀式供给方式的实验

高速烘缸内冷凝水形成的稳定水环层是热量传递的最主要阻力。分析烘缸内采用蒸汽汽刀式供给方式,对水环层进行剪切干扰,使原本稳定流动的水环层产生湍动的可行性;初步设计蒸汽汽刀式供给系统结构。为方便观察,用有机玻璃制成的筒体代替烘缸,用空气气刀模拟蒸汽汽刀进行了实验研究。实验结果表明,采用蒸汽汽刀式供给方式,使水环层产生湍动,降低水环层热量传递的阻力,增加传热效率,能够达到节能效果。     

有内筒造纸机烘缸的设计与实验

介绍了设置内筒的造纸机烘缸结构,其内筒筒壁上设置有均布的喷管,蒸汽通过喷管喷出冲击、扰动液环,提高传热效率,并进行了实验验证。计算出了内筒蒸汽的供给压力和温度,设计计算了喷管的相关参数。     

破坏烘缸内冷凝水环的两种方法

圆筒形烘缸内一般是空腔,设有蒸汽加热装置与冷凝水排出装置。当蒸汽的压力、流量稳定时,如何排出缸内的冷凝水是大家非常关心的问题。本文介绍两种国外改进烘缸结构、破坏冷凝水环、提高烘缸效率的方法供参考。1、安装击水棒在普通烘缸内,由于缸吸管的吸口与烘缸端面、缸壁均保持一段距离,所以烘缸内壁形成的水环不能被破坏。为此,CELGAR J·JUSTUS提出的改进设计如下,见图1、图2。     

烘缸内汽刀式供汽装置的研究现状及其设计

分析高速纸机烘缸在工作过程中,水蒸汽放热冷凝后形成水环的运动状态及其对烘缸热量传递过程的影响以及扰动对水环流动状态的影响;在此基础上,详细介绍了烘缸内汽刀式供汽装置的结构设计情况。通过该装置提供所谓的"汽刀"冲击水环,改变层液水环的运动状态,提高传热效率。     

旋转接头的应用效果

目前,绝大多数纸厂的蒸球、烘缸进汽装置都是随机配套的老式进汽头。从结构上看,进汽头采用石棉盘根密封,进汽管、冷凝水管采取硬接,进汽头轴线与蒸球、烘缸空心轴线同心度要求较高(虽然同心度可调,但实际调试较难)。且运转一段时间后,容易偏心,蒸汽在进汽头内腔部位不能达到完全互相隔离。因此,我厂在使用中时有不同程度的蒸汽泄漏,烘缸内冷凝水排泄不畅,影响纸页干燥,维修比较困难。近年来,我厂先后用DM—D型双向内管固定式旋转接头改装1575双网双缸纸机烘缸进汽头,     

密封良好的可调式虹吸管

虹吸管是烘缸的重要组成部份,虹吸管使用效果理想与否,直接关系到烘缸汽头的同心密封程度,烘缸内蒸汽冷凝水能否顺畅排除和检修工作难易、环境好劣等问题。目前,造纸烘缸采用的虹吸管形式,大致有如下几种: 1.大弧度虹吸管:自身密封性好,但由于虹吸管重力产生的力矩大,蒸汽头同心旋转密封将会上下偏移,加速密封件的磨损,导至蒸汽头严重漏汽,甚至虹吸管下垂与烘缸发生摩擦,丧失虹吸能力。     

提高纸机干燥部生产能力的措施

有的工厂由于对于燥的强化措施不了解,出现了一些问题。例如,某中型厂为了提高纸机干燥速度,把原来的生蒸汽管道与第一段烘缸出来的二次蒸汽管道接通(即图中A、B两处用管道连起来),想借此提高二段烘缸内蒸汽温度,加快干燥速度.由于第一段烘缸进汽与出汽没有压差,对冷凝水排出不利,总的干燥效率反而可能下降.因此有必要对纸机干燥部     

介绍一种蒸汽头

六十年代我厂安装了一台1092纸板机,因蒸汽头的压环和紧圈容易磨损,汽水管道热胀冷缩导致了外壳与转轴不同心。密封盘根产生单边松紧而有严重漏汽现象。另外,虹吸管两端压力差较小,烘缸冷凝水排除难度大,有时因紧圈磨损严重而未及时处理,使汽头外壳扭断而被迫停汽。78年我们分析了这些现象的原因,设计出如图1所示的蒸汽头,基本解决了以上所述的问题。     

烘缸虹吸管的性能

推导一种线性的分析模型,描述在旋转着的干燥烘缸中,边缘冷凝水流向圆周沟槽。这种模型包含烘缸速度、蒸汽压力、烘缸长度和冷凝水量的影响。模型假设冷凝水厚度不同的层流产生液压梯度。分析结果和在较大范围的冷凝水量与烘缸速度的实验数据之间取得良好的一致性。该分析用于说明操作条件对烘缸性能的影响。     

热泵供热系统在纸机干燥部的应用

本文用生产应用实例表明,在造纸机干燥部应用热泵供热系统能解决多段通汽系统中存在的问题.热泵供热系统能使蒸汽被循环使用,还能使纸机烘缸中的冷凝水通畅地排出;同时提高烘缸的传热强度,使蒸汽消耗量降低,热能利用充分.     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Analysis of benzo[a]pyrene in spiked fatty foods by second derivative synchronous spectrofluorimetry after microwave-assisted treatment of samples

A simple, rapid and inexpensive method has been developed for the determination of benzo[a     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. II: Certification study

This paper describes the second part of a project undertaken to develop certified mussel reference materials for paralytic shellfish poisoning toxins. In the first part two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin and decarbamoyl-saxitoxin in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the certification exercise. Fifteen laboratories participated in this certification study and were asked to measure saxitoxin and decarbamoyl-saxitoxin in rehydrated lyophilized mussel material and in a saxitoxin-enriched mussel material. The participants were allowed to use a method of their choice but with an extraction procedure to be strictly followed. The study included extra experiments to verify the detection limits for both saxitoxin and decarbamoyl-saxitoxin. Most participants (13 of 15) were able to meet all the criteria set for the certification study. Results for saxitoxin.2HCl yielded a certified mass fraction of <0.07 mg/kg in the rehydrated lyophilized mussels. Results obtained for decarbamoyl-saxitoxin.2HCl yielded a certified mass fraction of 1.59+/-0.20 mg/kg. The results for saxitoxin.2HCl in enriched blank mussel yielded a certified mass fraction of 0.48 +/- 0.06 mg/kg. These certified reference materials for paralytic shellfish poisoning toxins in lyophilized mussel material are the first available for laboratories to test their method for accuracy and performance.     

Announcing a new international peer-reviewed journal:Food Science and Human Wellness now accepting manuscript submission in English

<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of the     

Chinese CTP Market

According to Printing and Printing Equipment Industries Association of China（PEIAC）＇s statistics to the plate manufucturer in China, in 2013, the actual offset plate production has reached 346 million square meters in China. Among them, the CTP production volume was 245 million square meters, up by 11% than that of last year; the total sales of the CTP plate was 239 million square meters, up by 13%.     

Preparatory Work of Print China 2015 is Going Smoothly

正Held at Guangdong Modern International Exhibition Center,Print China 2015 will cover 7exhibition halls,besides the original Hall No.3,4,5,6,7,the newly built F zone of Hall 3 will be used too.The total area will be140,000 square meters.Hall 3:Offset and large printing equipment,package printing equipment,post press