BRIGHTNESS AND BLEACHABILITY OF THERMOMECHANICAL PULP

Several refining variables, including speed, consistency, specific ene rgy and plate pattern were investigated for their influence on pulp br ightness and bleachability during thermomechanical pulping. The result s showed that: 1) increasing speed and reducing consistency improved b oth brightness and bleachability; 2) changing plate pattern to a lower radial friction coefficient surface also improved brightness and blea chability; and 3) specific energy, however, had little effect on brigh tness. Among the variables studied, refiner speed was found to have th e most dominating effect AU these effects may be explained in terms of refining intensity and residence time in the refiner. A higher refini ng speed at an elevated temperature improved thermomechanical pulp qua lity balance between brightness and strength properties. This is a fun damental reason why the RTSTM process is able to produce a stronger, a nd yet brighter and easier to bleach pulp than conventional TMP pulp.