Low Consistency Refining of Mechanical Pulp: A Methodology to Relate Operating Conditions to Paper Properties

In this study we experimentally examined the effect of low consistency refining on mechanical pulp quality using a 56 cm (22 '') pilot disc refiner. Experiments included a wide range of operating conditions and different pulp freeness'. We proposed a method to correlate operating conditions to final paper properties. We demonstrate that the dimensionless power number increases linearly with the inverse of plate gap. We found that plate gap and specific energy are related to two key pulp characterization parameters, namely fibre length distribution and freeness. Further we found that tear strength, bulk and tensile index are related to both fibre length and freeness independent of refining conditions. Finally, we demonstrate that an optimal plate gap exists to achieve the maximum tensile increase at a minimum energy, and that the optimal gap is a function of the feed pulp freeness.