EFFECT OF PRETREATMENT PROCESSES ON KRAFT PULPING OF MIXED POPLAR

摘要

The pretreatment processes of green liquor pretreatment and pre-steaming followed by screw extrusion were applied in kraft pulping of mixed poplar. Brightness and strength of the pulps were obviously improved, and active alkaline dosage decreased. Compared with conventional kraft pulping, active alkaline charge decreased by 33%, and brightness, tensile index, bursting index, folding number of the pulps obtained in kraft pulping with green-liquor pretreatment followed by screw extrusion increased respectively 4.7%ISO, 11.3%, 30.4% and 88.3% at the similar pulp yield and the kappa numbers. Pulp yield and brightness of the pulp obtained in kraft pulping with pre-steaming followed by screw extrusion were respectively improved 2.9% and 2.6%ISO at the same active alkaline charge,and physical strength of the pulp decreased slightly.