纸张内部水分存在形式及其干燥特性研究
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摘要
利用低场核磁共振(LF-NMR)检测技术,对纸张内部水分存在形式及其干燥特性做了初步探索。结果表明,①依据所受束缚力的不同,纸张内部水分存在3种形式,即游离水、毛细管水和结合水;②结合水含量很少(约2%),且在干燥工段基本不发生变化,纸张干燥蒸发的主要是游离水和毛细管水,游离水所受束缚力小,干燥初期就开始大量蒸发,毛细管水所受束缚力大,在游离水蒸发完全时,才迅速蒸发;③依据蒸发水分的不同形式,以临界含水率为界,纸张干燥过程可以分为两个阶段:临界含水率以上为游离水干燥阶段,临界含水率以下为毛细管水干燥阶段。
In the current study, the existing forms of internal water in paper web and its drying characteristics during drying process were preliminarily explored by using LF-NMR detection technology.The experimental results showed: ①According to the different binding forces, there are three forms of internal water in paper web, i.e. free water, capillary water and bound water.②The bound water is very little(about 2%), and it is basically unchanged during drying process. The main evaporated water during paper drying process is free water and capillary water. Free water has little restraint and it is evaporated largely at the beginning of drying. Capillary water is strongly bound and evaporates rapidly after free water is evaporated completely.③According to the different forms of evaporating water, the drying process of paper can be divided into two stages i.e. free water drying stage(the moisture content of paper is greater than critical moisture content) and capillary water drying stage(the moisture content of paper is less than critical moisture content).
In the current study, the existing forms of internal water in paper web and its drying characteristics during drying process were preliminarily explored by using LF-NMR detection technology.The experimental results showed: ①According to the different binding forces, there are three forms of internal water in paper web, i.e. free water, capillary water and bound water.②The bound water is very little(about 2%), and it is basically unchanged during drying process. The main evaporated water during paper drying process is free water and capillary water. Free water has little restraint and it is evaporated largely at the beginning of drying. Capillary water is strongly bound and evaporates rapidly after free water is evaporated completely.③According to the different forms of evaporating water, the drying process of paper can be divided into two stages i.e. free water drying stage(the moisture content of paper is greater than critical moisture content) and capillary water drying stage(the moisture content of paper is less than critical moisture content).
引文
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[13] LI Jielin,LIU Hanwen,ZHOU Keping,et al.An LF-NMR study of the micro-structural deterioration of rocks under the effect of freeze-thaw cycles[J].Journal of Xi'an University of Science and Technology,2018(2):266.李杰林,刘汉文,周科平,等.冻融作用下岩石细观结构损伤的低场核磁共振研究[J].西安科技大学学报,2018(2):266.
[14] SONG Zhaopeng,WEI Shuo,HE Fan,et al.Analysis of moisture migration and drying characteristics of tobacco during flue-curing by low field NMR[J].Acta Tabacaria Sinica,2017,23(4):50.宋朝鹏,魏硕,贺帆,等.利用低场核磁共振分析烘烤过程烟叶水分迁移干燥特性[J].中国烟草学报,2017,23(4):50.
[15] MA Tianlan,WU Longguo,WANG Songlei,et al.Detection of tan-sheep meat tenderness based on low-field nuclear magnetic resonance[J].Science and Technology of Food Industry,2017,38(2):69.马天兰,吴龙国,王松磊,等.基于低场核磁共振技术检测冷鲜滩羊肉的嫩度[J].食品工业科技,2017,38(2):69.
[16] Sherwood T.The Drying of Solids-III Mechanism of the Drying of Pulp and Paper[J].Industrial & Engineering Chemistry,1930,22(2):132.
[2] KONG Lingbo,YU Changming,LIU Hongbin.Preliminary study on evaporation mechanism of moisture in paper during drying process[C]//The 15th National Conference on Drying Technology.Chengdu,2015:25.孔令波,俞昌铭,刘洪斌.干燥过程纸页内部水分蒸发机理初探[C]//第15届全国干燥技术交流会.成都,2015:25.
[3] CHEN Xiaobin,DONG Yunyuan,Zheng Qifu,et al.Kinetic Model and Numerical Simulation of Paper Drying Process Base on Boundary Layer Theory[J].Transactions of China Pulp and Paper,2017,32(3):37.陈晓彬,董云渊,郑启富,等.基于“边界层”理论的纸张干燥动力学模型及其数值仿真[J].中国造纸学报,2017,32(3):37.
[4] ZHOU Yanming,LIU Huanbin,LI Jigeng.The Dryer Section Modeling Based on Integrated Analysis of Material,Energy and Exergy Flows[J].Transaction of China Pulp and Paper,2014,29(1):33.周艳明,刘焕彬,李继庚.集成物流、能流和■流分析的纸机干燥部建模[J].中国造纸学报,2014,29(1):33.
[5] KONG Lingbo,LIU Huanbin,LI Jigeng,et al.Modeling and Simulation of Paper Machine Dryer Section Based on Its Process Flow[J].Transactions of China Pulp and Paper,2015,30(4):44.孔令波,刘焕彬,李继庚,等.基于工艺流程的纸机干燥部建模与模拟[J].中国造纸学报,2015,30(4):44.
[6] CHEN Xiaobin,LI Jigeng,ZHANG Zhanbo,et al.Online Measurement and Analysis of Drying Curve of a High-strength Corrugating Medium Machine[J].China Pulp and Paper,2014,33(8):7.陈晓彬,李继庚,张占波,等.高强瓦楞原纸干燥曲线在线测量与分析[J].中国造纸,2014,33(8):7.
[7] Heikkil? P.A Study on the Drying Process of Pigment Coated Webs[D].Finland:?bo Akademi University,1993:113.
[8] GHOSH A K.Fundamentals of paper drying-theory and application from industrial perspective[M].Croatia:InTech,2011:546.
[9] Karlsson M.Book 9:Papermaking Part 2:Drying[M].Finland:Finnish Paper Engineers Association and TAPPI,2000:41.
[10] HE Beihai.Principles and engineering of papermaking[M].3rd.ed.Beijing:China Light Industry Press,2010:281.何北海.造纸原理与工程[M].3版.北京:中国轻工业出版社,2010:281.
[11] TAN Tian′en,DOU Mei.Principles of Chemical Engineering Fourth Edition(Volume 2)[M].Beijing:Chemical Industry Press,2013:154.谭天恩,窦梅.化工原理第四版(下册)[M].北京:化学工业出版社,2013:154.
[12] JIANG Chao,HAN Jianzhong,FAN Jiali,et al.Rapid detection of adulterated milk by low field-nuclear magnetic resonance coupled with PCA method[J].Transactions of the CSAE,2010,26(9):340.姜潮,韩剑众,范佳利,等.低场核磁共振结合主成分分析法快速检测掺假牛乳[J].农业工程学报,2010,26(9):340.
[13] LI Jielin,LIU Hanwen,ZHOU Keping,et al.An LF-NMR study of the micro-structural deterioration of rocks under the effect of freeze-thaw cycles[J].Journal of Xi'an University of Science and Technology,2018(2):266.李杰林,刘汉文,周科平,等.冻融作用下岩石细观结构损伤的低场核磁共振研究[J].西安科技大学学报,2018(2):266.
[14] SONG Zhaopeng,WEI Shuo,HE Fan,et al.Analysis of moisture migration and drying characteristics of tobacco during flue-curing by low field NMR[J].Acta Tabacaria Sinica,2017,23(4):50.宋朝鹏,魏硕,贺帆,等.利用低场核磁共振分析烘烤过程烟叶水分迁移干燥特性[J].中国烟草学报,2017,23(4):50.
[15] MA Tianlan,WU Longguo,WANG Songlei,et al.Detection of tan-sheep meat tenderness based on low-field nuclear magnetic resonance[J].Science and Technology of Food Industry,2017,38(2):69.马天兰,吴龙国,王松磊,等.基于低场核磁共振技术检测冷鲜滩羊肉的嫩度[J].食品工业科技,2017,38(2):69.
[16] Sherwood T.The Drying of Solids-III Mechanism of the Drying of Pulp and Paper[J].Industrial & Engineering Chemistry,1930,22(2):132.