Comparative evaluation of conical and double disk refiners: Effects of operating mode, refining intensity, and device geometry on energy consumption and paper properties, TAPPI Journal August 2026

ABSTRACT: This study investigates the effects of refiner operating mode and refining intensity adjusted via pulp flow rate, applied power, and refiner speed on the refining characteristics of high-yield southern softwood. We compared Valmet’s OptiFiner PRO (conical) and DD6700 (double disk) refiners under matched specific edge load (SEL)
conditions. Batch and one-pass modes were evaluated for their impact on energy efficiency and physical paper properties. The results showed that while SEL provides a useful baseline, it does not fully account for differences in refiner geometry, particularly angular parameters. With the chosen plate sets, C-factor analysis revealed that the OptiFiner PRO delivers a lower number of fiber impacts at a higher intensity per impact compared to DD6700 at similar SEL, influencing fiber length, short-span compression test (STFI) index, and tear strength development. These findings offer actionable insights for mills seeking to optimize refining efficiency and cost. In summary, conical refiners may provide advantages in compression strength at mid-range energies, while double disk refiners maintain higher tear strength at elevated energies due to better fiber length preservation.

Application: Readers can use the information in this study to gain a fundamental understanding of the similarities and differences between conical and double disk refining technologies, particularly in terms of energy efficiency and strength development for high yield southern softwood used in unbleached linerboard and kraft bag production. This research provides valuable insights for mills looking to update their machinery and improve their refining
processes to reduce carbon footprint and enhance fiber strength.