On the Application of Grinding and Thermomechanical Pulp Refining, 2007 International Mechanical Pulping Conference

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Surface mechanical treatment of pulp fibers using grit material in thermomechanical pulp (TMP) refining after the first-stage refining and the subsequent refining of the treated pulp were studied. The surface mechanical treatment was performed using an ultra-fine friction grinder. The grit size of the grinding stone, the intensity of treatment and the rotational speed were optimized to accomplish fast development and to minimize the shortening of pulp fibers. The subsequent refining was carried out using a wing defibrator operated under typical TMP refining conditions. According to the results, surface mechanical treatment using a grinding stone with a grit diameter of 297-420 µm, operated at a contact point of the stones and a high rotational speed of 1500 rpm, provided an efficient disruption of pulp fibers with minimized cutting. Disruption of the pulp about 20% of total energy consumption produced a promising fracture of fiber cell wall for the further development. In the subsequent refining, the disrupted pulp was found to result in faster development of pulp freeness, while requiring 37% less energy. Laboratory sheets showed no significant differences in properties between the disrupted and non-disrupted pulps at a given freeness.