Effect of compression on refining energy and pulp properties of birch TMP

The influence of chip conditioning by across-the-grain compression on therm omechanical pulping of white birch has been investigated. Scanning electron microscopic examination indicated that cell wail delamination particularly in P-S-1 and/or S-1-S-2 zones could be induced by static compression. Refi ning of platen-pressed chips showed about 9% reduction in refining energy a nd substantial improvement in tensile and burst indices, when compared with the standard TMP using screw-pressed chips. There was no noticeable loss i n tear index within a freeness range of 250 to 400 CSF. The benefits of chi p pressing were more significant when compared with the refining of unpress ed chips.