Impact of sulfidity on the kraft pulping of eucalyptus

This study aimed to evaluate the influence of white liquor sulfidity on the efficiency of the kraft pulping process. For this study, Eucalyptus spp. chips were used. Laboratory cooking with variable sulfidity levels (0 to 40% at 5% intervals) was conducted under previously optimized conditions, aiming to obtain pulp with a Kappa number of 18 ± 0.9 and residual effective alkali between 9 and 12 gL-1. At the end of each cook, Kappa number, solids generation, specific wood, and alkali consumption were evaluated. The sulfidity variation in white liquor influenced all analyzed parameters, and concerning the specific wood consumption, a distinct behavior was observed for the low sulfidity (S ≤ 19.52%) and high sulfidity regions (S ˃ 19.52%). Based on the obtained results, the production of eucalyptus kraft pulp with white liquor sulfidity of approximately 20% is recommended.