Migration of wood extractives in the fiberline of birch kraft pulp mill with ECF bleaching
- May 20
- 2 min read
Lauri Leskinen, Elena Melnik, E. Yee Lim, Mery Lempinen, Nelli Kaskirinne, Simo Levan, Hanna Romppainen, Aaro Uusitalo, Jinze Dou
Abstract: Pressure to decrease freshwater consumption at pulp mills is causing an increase in deposit problems, as higher probability of scaling and precipitation is contributed to the increasing concentrations of these compounds in the process streams. The goal of this study was to characterize the composition of a dryer tank deposit from a Nordic hardwood kraft mill and identify the reasons behind its formation. A single solvent ethyl acetate extraction system was proposed instead of the established three solvent sequestional extraction sequence with dichloromethane, acetone, and water, respectively. A total of 41 compounds were identified in the ethyl acetate extract of the dryer tank deposit compared to 43 compounds identified using the traditional method. GC–MS identifiable compounds consisted mainly of wood extractives and auxilary chemicals used in pulping. FTIR confirmed the assumption, that talc is the major contributor to the bulk of the deposit. SEM imaging revealed the morphological features of the deposit and supported the findings from FTIR.
Ethyl acetate extraction was used to study the lipophilic extractable compounds in pulps and pulp liquids at different stages of bleaching sequence to shed light on the circulation of these compounds in the process streams. The major findings included a speculative hypothesis that accumulation of lipophilic extractives to the white water was influencing the content of lipophilic extractives in the finally bleached pulp. In the future, this knowledge could be used to optimize pulp bleaching and water circulation to limit the formation of pitch deposits and to enhance pulp and sheet forming properties.
