RTSTM is a new Low Retention, High Temperatureand High Speed TMP pulping method developed by Andritz. While the pulp quality is kept the same as conventional TMP, the energy is 15-17% less than the conventional TMP.Extensive studies were conducted to evaluate the development of pine pulp properties and energy requirements using two different thermomechanical refining processes at a southern U. S. paper mill.The processes included both a low intensity (TMP) and a high intensity (RTSTM) refining configuration.The pulps produced with the RTS process had 15%-17% lower energy consumption compared to TMP pulps produced at similar freeness and handsheet physical properties. Despite similar average fiber length results between the two processes, the low intensity pulps had a higher percent by weight of fiber retained on the Bauer McNett 14/28 fractions, whereas the high intensity pulps had a higher percent by weight retained on the middle fractions. Calendered newsprint produced from the high intensity pulp had a lower roughness, which may be related to the lower fiber size distribution. Light was thrown on this finding by porometry measurements of the newsprint, which revealed a slightly lower pore size distribution from paper produced with the higher intensity pulp. Standard ink printing tests, however, provided similar results between newsprint paper produced from the TMP and RTSTM processes.

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