Abstract
AbstractThe hypothesis was that low residual alkali after cooking would cause lignin re-precipitation during washing and in turn affect the subsequent oxygen delignification stage negatively. To test the hypothesis, kraft cooks were performed in lab-scale to different residual alkali levels, ranging from 5 to 15 g/L and the pulps were subjected to washing with either water or 0.1 M NaOH and then oxygen delignified. The results show that even at low residual alkali and washing with water, the pH in the liquor after washing was above 11 which is sufficiently high to keep lignin in solution. No effect of residual alkali level was observed on the performance of the oxygen delignification stage.
Funder
Bo Rydins Stiftelse för Vetenskaplig Forskning
Royal Institute of Technology
Publisher
Springer Science and Business Media LLC
Reference24 articles.
1. Alén R, Patja P, Sjöström E (1979) Carbon dioxide precipitation of lignin from pine kraft black liquor. Tappi 62:108
2. Andrade M, Colodette J, Oliveira F (2013) Evaluation of bleachability on pine and eucalyptus kraft pulps. Cerne 19:433–439
3. Brännvall E, Rönnols J (2021) Analysis of entrapped and free liquor to gain new insights into kraft pulping. Cellulose (2021). https://doi.org/10.1007/s10570-020-03651-3
4. Colodette J, Gomide J, Russel G, Jääskeläinen A, Argyropoulos D (2002) Influence of pulping conditions on eucalyptus kraft pulp yield, quality, and bleachability. Tappi J 1:14–20
5. Dang B, Brelid H, Theliander H (2016) The impact of ionic strength on the molecular weight distribution (MWD) of lignin dissolved during softwood kraft cooking in a flow-through reactor. Holzforschung 70:495–501