纸幅横向厚度控制系统的应用

大宇制纸有限公司在引进纸幅横向厚度控制系统之前,一直采用手动调整冷却风量和用油加热辊面来控制纸幅横向厚度,操作比较困难。纸幅的横向厚度偏差2-sigma值通常在2.0以上,时常造成纸幅横向厚度不均而产生残次品。每次纸机停机或发生断纸,从再次开机或接纸开始到纸幅横向厚度调整达到预定目标值,需要用20～30min,调整时间较长。使用纸幅横向厚度控制系统后,改善了纸幅横向厚度偏差,提高了产品质量,2-sigma值偏差可以控制在0.19～0.5之间,停机或断纸后再次开机,纸幅横向厚度调整达到预定目标值只需要用7～10min。1新系统原理纸幅横向厚度控…     

气垫干燥结构简介

气垫干燥是靠热风气流使纸幅在悬浮的状态下加热于燥，特别适合定量较大的纸板干燥。我厂于1992年引进了瑞典FLAKT公司专利生产的一套该设备，下面对其构造作一简单介绍。整个气垫干燥设备由导辊、热风箱及框架、送风回风系统及引纸装置等组成。如图1所示1导辊部分在整个气垫干燥设备的前后各设有一组导辊，其作用在于利用辊简引导纸幅回头重新进人气垫子燥加热脱水。辊组各辊之间呈垂直排列，辊简数量由热风箱的层数确定。导辊两端的轴承座装在一个整体框架上，纸相在经过热风箱时不会跑们。两辊组由一台12．7kW电机带动。经万向联轴器…     

热压工艺中的“蒸汽喷雾压光法”

成纸的表面特性，长期来都是通过多压区高线压的压光机而达到纸资表面平滑和光洁的要求。近年来市场对纸的适印性要求越来越高。国外普遍采用热压法（HotCalender），其中有辊内以一定温度的水、油作为媒体的对流加热，诱电感应发热，辊外两侧双向感应加热以及本文所述的蒸汽喷雾加热。1蒸汽啸奔装置蒸汽喷雾加热装置简单，在压光机的进纸侧前登蒸汽喷箱，对纸面横幅均匀地直接进行低压热蒸汽喷雾（低压蒸汽应控制在90℃左右）。优点是：当纸面受热时亦调整了水分，在通过压区后纸面的光洁度、平滑度都有明显改善。这实际是“熨烙”作用。…     

可控中高辊控制系统

胶印新闻纸的压光关系到提高纸的平滑度、光泽度和厚度均匀性,必须很好地解决,为此,我公司从美国引进了可控中高辊,即NIPCO辊。通过精心安装调试,该系统能自动调节各个压区的液压缸的油压,来改变辊的表面平均线压力,以达到调整纸面质量的作用,本文对该系统的控制系统作一个概括性的介绍。INIPCO＄控制系统的组成该控制系统是由操作显示单元,控制单元,伺服放大单元,油压控制单元,逻辑控制单元,增量控制器六部分组成。系统如图1所示。2NIPCO辊的控制原理按照正确的操作顺序,NIPCO辊可以工作在四种状态,即张开、闭合、…     

解决纸边厚薄不均的小窍门

正浆纸技术2018-02-06(作者何灿光)报道:广州造纸股份有限公司8号机升级改造时横幅厚度控制采用了新的软压光系统,采用升级改造前的ABB扫描架。软压光系统由上辊的热辊和底辊的软辊组成,软辊由54个加压元件组成54个压区,对横幅厚度进行调整。纸边厚度存在的问题纸页经软压光到卷取后,卷取轴上的纸出现皱纹,检测发现纸边厚度情况如图1纸边约10mm     

IMPACT定量水份厚度控制系统的应用与维修

浅析了IMPACT定量水份厚度控制系统的测量控制原理及特点,综述了系统在纸机成纸质量控制上的应用,初步总结了在纸机生产过程中该系统的维修经验。     

纸机网案改进的尝试

我厂5#、6#纸机网案属典型低速长网造纸机的网案结构，网案长10．20m，铜网长22．56m，网宽2.03m。网案采用24个案辊，6个真空吸水箱及双室真空伏辊作为网部的脱水元件，主要用来生产卷烟纸系列产品，车速120～140m／min。为了提高成纸质量，延长铜网的使用寿命，我们对这两台纸机的网案进行了一些改进。1对纸机案辊的改进案辊是纸幅成形的脱水元件，它的结构和运行状况对纸页匀度，纸张质量影响较大。案辊的作用不仅使纸料脱水，而且支承铜网及网上的纸料，以形成一个平整的网案，供纸页滤水成形。案辊是由铜网拖动的，而铜网对案辊只有很…     

ZWJ_1-1880复卷机气动卸辊装置的设计

ZWJ1－1880复卷机将纸辊分切后，由人推下去，完成卸辊。我们为它设计了一种气动装置来自动完成卸辊工序。其构成如图1所示。图1气动卸辊装置示意图1、2－支撑辊A、B3－纸辊4－气缸1可行性分析与计算1．1基本情况根据纸辑的实际规格，我们选择最大的纸辊作为研究对象。纸辊最大规格为850mm，质量800kg。1．1．1受力分析纸辊放在支撑辊A、B上，处于平衡状态。在纸辊左侧施加推力声，作用点在E点，方向垂直于O1O2。在推动纸辊转动的瞬间（纸辊刚刚脱离支撑辊A，只靠辊B支撑），纸辊的受力分析如图2。O1O3＝0．425m，O2O3＝0．160m，O2…     

印刷机上进行双张控制的方法

印刷时，纸张必须逐张地进入印刷机，不能有双张或多张纸张进入印刷机的现象出现。本文详细介绍了现在印刷机上采用的双张控制方法，分析了各种双张控制器的工作原理以及各自的特点。一、机电式双张控制器这是一种使用最为普遍的双张控制器,其基本原理是：当出现双张时，纸张的厚度会发生变化，因此检测厚度就可以判定出现的是不是双张。根据其机械结构的不同，又可以分为多种型式。1.摆动型式这种检测装置一般安装在送纸辊的上方，如图1所示。当递纸吸嘴将纸张向送纸辊递送时，压纸轮上抬让纸，凸轮3的高面与滚子4接触，摆杆5通过滑座6、调…     

高频电磁感应加热技术在接装纸鼓轮中的应用

针对MOLINS卷接机组中原接装纸鼓轮加热系统存在的缺点,采用高频电磁感应加热技术对接装纸鼓轮加热系统进行了改进。论述了高频电磁感应加热原理以及该技术在接装纸鼓轮加热中的实现。     

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.     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPL C with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether)analysed in the same products in the context of a previous study.     

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.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.