Development of Spruce Fiber Properties by a Combination of a Pressurized Compressive Pretreatment and High Intensity Refining, 1999 International Mechanical Pulping Conference Proceedings

K.-A. Kure

PFI - Norwegian Pulp and Paper

Research Institute

G. Dahlqvist

Andritz Inc

M.J. SABOURIN

Norske Skog Research

T. HELLE

Department of Chemical Engineering

NTNU - Norwegian University of

Science and Technology

The study shows that a pressurized compressive pretreatment combined with high intensity refining is an efficient way to save energy in thermomechanical pulping. Compared at a given specific energy consumption level this combination yielded better strength and optical properties and less shives compared to conventional TMP. The pretreatment resulted in a large fraction of partially defibrated fibres, predominately latewood fibres. The earlywood fibres were more deformed, but less defibrated. Rising refining intensity by increasing rotational speed in the range 1800-2900 rpm increased the fraction of fibres with longitudinal splits in the fibre wall. These fibres will collapse easier and form a smoother paper surface. No significant reduction in fibre length was found when raising refining intensity after the compression pretreatment. The results indicate that it may to some extent be possible to preserve fibre length if the fibres are partially defibrated prior to primary refining.