Article Comparative Analysis of Ultra-Fine Bar Refining and Valley Beating on Softwood and Hardwood Kraft Pulps: Implications for Fiber Integrity and Paper Strength Enhancement Hyeong-Hun Park 1 , Chul-Hwan Kim 2, * , Ju-Hyun Park 1 , Min-Sik Park 1 and Jae-Sang Lee 3
1 Department of Forest Products, Gyeongsang National University, Jinju 52828, Republic of Korea; bhh1217@naver.com (H.-H.P.); zdrxft1215@naver.com (J.-H.P.); tig05042@naver.com (M.-S.P.) 2 Department of Forest Products, Institute of Agriculture and Life Science (IALS), Gyeongsang National University, Jinju 52828, Republic of Korea 3 Department of Pulp&Paper Chemical Engineering, Gyeongsang National University, Jinju 52828, Republic of Korea; dmh6780@naver.com * Correspondence: jameskim@gnu.ac.kr; Tel.: +82-10943078896 Abstract This study compared the effects of refining with an ultra-fine bar plate and Valley beat- ing on softwood (SwBKP) and hardwood (HwBKP) bleached kraft pulps. Ultra-fine bar refining reduced pulp freeness from 700 mL to 200 mL CSF in just 10 min for both SwBKP and HwBKP, whereas Valley beating required over 60 min to reach comparable freeness levels. At equivalent freeness (e.g., 300 mL CSF), refining resulted in a tensile strength increase of approximately 35% for SwBKP and 20% for HwBKP compared to beating. In addition, refining delivered higher burst and tear strengths across all tested freeness levels, while better preserving fiber length. The results clearly demonstrate that refining with an ultra-fine bar plate achieves faster development of desirable paper properties and superior strength enhancement relative to Valley beating for both softwood and hardwood kraft pulps. These findings emphasize the importance of direct refining trials and plate optimization for improving pulp quality and energy efficiency in papermaking.
Keywords: beating; refining; ultra-fine bar plate; fibrillation; fiber cutting
Received: 23 July 2025 Revised: 18 August 2025 Accepted: 18 August 2025 Published: 20 August 2025
1. Introduction Mechanical treatment of pulp is a pivotal step in the papermaking industry, profoundly influencing the properties of the final paper product. In this study, mechanical treatment refers specifically to the processes of beating and refining, which are applied to alter pulp fiber morphology and enhance paper performance [1,2]. This research utilizes two types of mechanical treatment equipment: the Valley beater, a laboratory-scale device that enables controlled and reproducible fiber modification, and a disc refiner equipped with an ultra-fine bar plate, designed for industrial-scale refining with enhanced energy efficiency and precision. Beating and refining are essential mechanical processes for modifying pulp fiber properties and ultimately improving paper quality [1]. Both processes expose pulp fibers to a combination of shear, compression, and bending forces, resulting in external and internal fibrillation as well as fiber shortening [3,4], while shear forces mainly cause fiber cutting, compression, and bending enhance fibrillation, thereby increasing the surface area available for inter-fiber bonding and improving the strength properties of the resulting
Citation: Park, H.-H.; Kim, C.-H.; Park, J.-H.; Park, M.-S.; Lee, J.-S. Comparative Analysis of Ultra-Fine Bar Refining and Valley Beating on Softwood and Hardwood Kraft Pulps: Implications for Fiber Integrity and Paper Strength Enhancement. Appl. Sci. 2025 , 15 , 9160. https://doi.org/ 10.3390/app15169160 Copyright: © 2025 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/).
Appl. Sci. 2025 , 15 , 9160
https://doi.org/10.3390/app15169160
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