Fiber development in chemimechanical pulp refining

A second-order PLS model has been calculated to study the impact of two-stage refining on the standard hand-sheet properties of a chemimechanical pulp as well as the effect on fiber length distribution and whole pulp specific surface. For a certain ratio of specific energy to refining intensity in the first stage, specific surface can be developed without loss in average fiber length. Fine material is peeled primarily from the middle fiber fractions in the first stage of refining, when high energy levels are distributed over a large number of impacts. While increases in refining intensity may be substituted for increases in applied energy to maintain adequate fiber length, whole pulp specific surface benefits most from higher energy levels applied at low intensity. Minimizing energy requirements by increasing intensity in the first refining stage is therefore better suited to the stiffer fibers common to TMP pulping.