NSSC Process Optimization: I. Pulps Quality, 1998 Pulping Conference Proceedings

The objective of this work was to obtain the best physical properties of NSSC pulps, using low charges of chemical products. The experimental design did examine four variables at five levels (Central Composite Design CCD= 29 runs, five central points). Minimum and maximum limits of the independent variables were established using mill conditions as set point values. Variables studied were: cooking time (10 to 30 minutes), cooking temperature (154 to 186ºC), sodium sulfite (4 to 12% o.d.) and sodium carbonate charges on wood (0 to 3% o.d.). Each property was evaluated by comparison with the mill reference data (yield: 80%, 260 CSF, tensile index: 38 N.m/g). Cooking conditions for highest mechanical properties are: temperature of 186ºC, cooking time of 30 minutes, 11,6% of sodium sulfite and 3,05% of sodium carbonate on o.d. wood. These conditions imply important pulp brightness and yield reductions. Pilot plant trials were done to verify the laboratory results and the found equations. Four pulps were manufactured, using Spanish poplar as raw material. On these pulps, physical testing on 60 g/m2 handsheets and typical corrugated board tests on 120 g/m2 handsheets (CMT, RCT, STFI) were completed.