Improving Reaction Selectivity with NaOH Charges and Reaction Time in the Medium Consistency Oxygen Delignification Process

As more delignification is targeted, fiber degradation becomes a main issue in the pulping process. Sodium hydroxide (NaOH) is highly related to pulp quality in the medium consistency oxygen delignification process. Accordingly, the purpose of this research was to study the effect of NaOH charges and reaction time on reaction selectivity during the pulping process through medium consistency oxygen delignification. This research used Eucalyptus pelita and Acacia mangium pulp with a kappa number (KaNo) of 17–18. The medium consistency oxygen delignification process condition included a temperature of 80°C and oxygen pressure of 1 bar, while the reaction times were 20, 40, 60, 80, and 100 min. The NaOH charges were 5, 10, 15, 20, and 25 kg/t of pulp. The analysis parameters used were KaNo and viscosity. The variation in reaction time did not show a significant change in KaNo. The increase in reaction time and NaOH charge variations, meanwhile, can reduce pulp viscosity. Higher NaOH values significantly increased the delignification degree, and the higher NaOH charges and reaction times together lowered the degree of polymerization (DP). The variation in reaction time indicated that with a longer reaction time, the lower the DP, and with a higher NaOH charge and longer reaction time, the lower the reaction selectivity.