KRAFT PULPING OF THE MAIN HARDWOODS USED AROUND THE WORLD FOR PULP AND PAPER PRODUCTION

摘要

The objective of this work is to evaluate some of the main hardwoods used around the world for pulp production. For that, we studied seven species from different world regions: Eucalyptus grandis x Eucalyptus urophylla (6 years, Brazil), Eucalyptus globulus (12 years, Chile), Eucalyptus nitens (12 years, Chile), Acacia mangium (6 years, Indonesia), Acacia crassicarpa (6 years, Indonesia), Populus tremuloides (55 years, Canada) and Betula pendula (67 years, Finland). Chemical characteristics and basic density were determined for each material. Kraft pulping was performed applying 5 different levels of active alkali: 16, 18, 20, 22 and 24% (NaOH based). The others pulping conditions were sulphidity of 25%, 90 minutes for heating and 60 minutes on constant maximum temperature of 166°C. The results show that E. globulus is the densest material and P. tremuloides presents the lowest density, while the highest lignin proportion was found on A. crassicarpa. On pulping, the wood of P. tremuloides was the easiest to remove lignin, while A. crassicarpa had the most difficult delignification. In addition, P. tremuloides' pulping presented the highest yields and best selectivity, and the wood of A. mangium had the lowest alkali consumption.