Birch CTMP and TMP - Refining conditions determine the pulp and fiber fraction quality at a given chemical level

摘要

The CTMP and TMP pilot trials carried out using birch at different alkaline levels showed that the refining conditions themselves had the greatest effect on the CTMP properties at constant chemical consumption level. The fiber length was easily controlled between 0.6 and 1.1 mm by rotation speed and/or plate type and refining mode (SD or DD) with KCL's pilot 44" refiner. The low refining intensity and the highest possible fiber length always gave the highest tensile index at a given bulk. The gain in tensile was at least 20 to 45%. Naturally the scattering properties were the opposite. This behavior is analogous with that reported earlier for spruce pulps and their fiber lengths. The refining conditions and therefore fiber length had a much greater effect than the dosing point of the alkali to either the chips or the pulp in bleaching. The recommendation for comparing any hardwood species or processes is that the most suitable refining conditions are first found to avoid even minor fiber cutting. The fiber fractions developed by refining with birch the same way as has been reported for spruce TMP. The lower refining intensity at the 1st stage (higher fiber length) resulted in reduced fiber bonding properties (BMcN +48), but improved the bonding properties of the shorter fiber fractions and fines (BMcN -48). The latter two fractions therefore produced high tensile index at a given bulk in "high fiber length" birch CTMP.