Comparative Analysis of Ultra-Fine Bar Refining and Valley Beating on Softwood and Hardwood Kraft Pulps: Implications for Fiber Integrity and Paper Strength Enhancement

Abstract

This study compared the effects of refining with an ultra-fine bar plate and Valley beating 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.