processes
Article Theoretical Estimation of Evaporation Heat in Paper Drying Process Based on Drying Curve
Xiaobin Chen 1,2,3, *, Qifu Zheng 1, * and Yunyuan Dong 1
1 College of Chemical and Material Engineering, Quzhou University, Quzhou 324000, China; yunyuandong@qzc.edu.cn 2 Postdoctoral Workstation, Shanying International Holding Co., Ma’anshan 243000, China 3 Guangdong Provincial Key Lab of Green Chemical Product Technology, South China University of Technology, Guangzhou 510640, China * Correspondence: xiaobinchen@qzc.edu.cn (X.C.); zqf@qzc.edu.cn (Q.Z.) Abstract: At present, the theoretical estimation of paper web’s evaporation heat is based on sorption isothermals. The measuring conditions are harsh, and the test speed is slow. This paper attempts to explore a theoretical method which can quickly determine the evaporation heat of paper web. During the new method, based on the measurement of the paper drying curve, the theoretical estimation model of paper evaporation heat was obtained by deducing the mechanism of heat and mass transfer. Compared with the traditional method based on sorption isothermals, the new model based on the drying curve has some advantages in measurement speed and easy access to basic data. Finally, the paper verifies the reliability of the model from two application scenarios of the laboratory and production line.
Keywords: paper drying process; modeling; evaporation heat; energy
Citation: Chen, X.; Zheng, Q.; Dong, Y. Theoretical Estimation of Evaporation Heat in Paper Drying Process Based on Drying Curve. Processes 2021 , 9 , 1117. https:// doi.org/10.3390/pr9071117
1. Introduction Paper is a kind of hygroscopic material with a porous structure, mainly composed of fibers and other solid particles, such as fillers, sizing materials, additives and so on. Paper products play a significant role in every area of human activity, such as the record- ing, storage and dissemination of information, wrapping and packaging, writing and printing and so on. Papermaking is a basic raw material industry, closely related to the national economy. The paper-making process is essentially a very large dewatering operation. The major sections of the paper machine consist of: the forming section, press section and dryer section. The dryer section removes between 1.1–1.3 kg of water per kg of paper production, as compared with the 200 and 2.6 kg removed in the forming and press section [1]. Although the dryer section is responsible for a small fraction of total dewatering, it is the major energy consumer in the paper mill because porous and hygroscopic pulp fibers have hard- to-remove water that is considered to be located in the fiber cell wall and trapped in the fiber network geometry. According to the report prepared by the Institute of Paper Science and Technology (IPST), 61.9% of the total energy required for paper making is consumed in the paper drying process [2], and about 65% of the thermal energy is used for water evaporation based on Chen’s investigation [3,4]. In spite of its key role in papermaking and its high energy consumption—taking approximately 60% of the total physical length and accounting for almost 40% of the total capital cost of a common paper machine—paper drying is arguably the least understood papermaking operation. Perhaps the reason is the complexity of the paper drying process that involves heat transfer, evaporation, and the water removal process where steam pressure, air conditions, and condensate removal play key roles in determining the drying capacity and final product quality. The papermakers
Academic Editors: Evangelos Tsotsas, Zhiqiang Sun, Sheng Yang and Yi Ma
Received: 3 May 2021 Accepted: 25 June 2021 Published: 28 June 2021
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Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).
Processes 2021 , 9 , 1117. https://doi.org/10.3390/pr9071117
https://www.mdpi.com/journal/processes
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