| Abstract: | The purpose of this study was to compare plate and conical refiner fillings in refining of softwood and hardwood pulp fibers. Contrary to expectations,better tensile strength values were achieved when BSW was refined with conical fillings and the development of strength Was found to be insensitive to variations in refining intensity. A bar microprocile was measured with the aid of a profilometer. The leading edges of conicalfilling bars.were found to be rounder. A possible reason for the better tensile strength of pulp refined with conical fillings is that the round edge helps large SW fiber flocs to enter the space between the bars, resulting in less heterogeneous or more efficient treatment of fibers.The recorded gap closure values supported the above interpretation. The gap between conical fillings was found to become wider when pulp consistency and thus fiber flocculation increased, whereas increased pulp consistency decreased the gap between plate fillings, which was further reflected as increased fiber cutting. The reduction in fiber length was proportional to the increase in gap closure,supporting the earlier theory that fibers are squeezed and crushed between the bars. More attention should be paid to the wear of filling materials when refining BSW. A filling material which wears so that the bar edges are rounded would seem to promote high tensile strength and high average fiber length. |
